commit 9980d4abb843dbb9ef47488adb1c2017ca4d4703
parent e67c37eeb3541be5e5555d963cd54c066d89b772
Author: Amit Dutta <amitdutta4255@gmail.com>
Date: Fri, 24 Oct 2025 20:47:00 +0530
luc
Diffstat:
6 files changed, 463 insertions(+), 1 deletion(-)
diff --git a/docs/index.html b/docs/index.html
@@ -720,7 +720,7 @@ int main()
<div class="flex items-center">
<svg class="w-6 h-6 text-blue-500 mr-4 flex-shrink-0" fill="none" stroke="currentColor" viewBox="0 0 24 24" xmlns="http://www.w3.org/2000/svg"><path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M3 7v10a2 2 0 002 2h14a2 2 0 002-2V9a2 2 0 00-2-2h-6l-2-2H5a2 2 0 00-2 2z"></path></svg>
<span class="font-medium text-gray-800">letusc</span>
- <span class="ml-2 text-sm text-gray-500">(52 files)</span>
+ <span class="ml-2 text-sm text-gray-500">(57 files)</span>
</div>
<div class="flex items-center space-x-4">
<a href="https://github.com/notamitgamer/bsc/tree/main/letusc" target="_blank" class="p-1 rounded-full text-gray-500 hover:bg-gray-200 hover:text-gray-800 transition-colors" onclick="event.stopPropagation()" title="View folder on GitHub">
@@ -3337,6 +3337,273 @@ int main()
}</code></pre>
</div>
</li>
+
+ <li>
+ <div class="flex items-center p-3 pl-8 hover:bg-gray-50 transition-colors duration-200">
+ <svg class="w-6 h-6 text-green-500 mr-4 flex-shrink-0" fill="none" stroke="currentColor" viewBox="0 0 24 24" xmlns="http://www.w3.org/2000/svg"><path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M7 21h10a2 2 0 002-2V9.414a1 1 0 00-.293-.707l-5.414-5.414A1 1 0 0012.586 3H7a2 2 0 00-2 2v14a2 2 0 002 2z"></path></svg>
+ <span class="text-gray-700">lucproblem008.c</span>
+ <div class="ml-auto flex items-center space-x-4">
+ <a href="https://github.com/notamitgamer/bsc/blob/main/letusc/lucproblem008.c" target="_blank" class="p-1 rounded-full text-gray-500 hover:bg-gray-200 hover:text-gray-800 transition-colors" title="View file on GitHub">
+ <svg class="w-6 h-6" fill="currentColor" viewBox="0 0 24 24" aria-hidden="true"><path fill-rule="evenodd" d="M12 2C6.477 2 2 6.477 2 12c0 4.418 2.865 8.168 6.839 9.492.5.092.682-.217.682-.482 0-.237-.009-.868-.014-1.703-2.782.605-3.369-1.343-3.369-1.343-.454-1.158-1.11-1.466-1.11-1.466-.908-.62.069-.608.069-.608 1.003.07 1.531 1.032 1.531 1.032.892 1.53 2.341 1.088 2.91.832.092-.647.35-1.088.636-1.338-2.22-.253-4.555-1.113-4.555-4.951 0-1.093.39-1.988 1.031-2.688-.103-.253-.446-1.272.098-2.65 0 0 .84-.27 2.75 1.026A9.564 9.564 0 0112 6.844c.85.004 1.705.115 2.504.337 1.909-1.296 2.747-1.027 2.747-1.027.546 1.379.203 2.398.1 2.651.64.7 1.03 1.595 1.03 2.688 0 3.848-2.338 4.695-4.566 4.942.359.308.678.92.678 1.855 0 1.338-.012 2.419-.012 2.747 0 .268.18.58.688.482A10.001 10.001 0 0022 12c0-5.523-4.477-10-10-10z" clip-rule="evenodd"></path></svg>
+ </a>
+ <button onclick="showCode('code-letusc-lucproblem008_c', 'lucproblem008.c')" class="text-green-600 font-semibold text-sm hover:underline">View Code</button>
+ </div>
+ </div>
+ <div id="code-letusc-lucproblem008_c" class="hidden" data-github-url="https://github.com/notamitgamer/bsc/blob/main/letusc/lucproblem008.c">
+ <pre><code class="language-c">/* Write a problem to print all the prime numbers from 1 to 300. */
+/* Author - Amit Dutta, Date - 24th OCT, 2025 */
+/* Let Us C, Chap - 6, Page - 101, Problem 6.1 */
+
+// Method: Trial Division (Optimized to check up to sqrt(N))
+
+#include <stdio.h>
+#include <math.h>
+#include <stdbool.h>
+
+#define LIMIT 300
+
+int main()
+{
+ printf("Prime numbers from 1 to 300 : 2"); // as 2 is the only even prime number
+ for (int i = 3; i <= LIMIT; i += 2) // skipping all other even number
+ {
+ int n = (int)sqrt(i);
+ bool prime = true;
+
+ for (int j = 3; j <= n; j += 2)
+ // an odd number is only devisable by another odd number.
+ // so, skipping even number.
+ {
+ if (i % j == 0)
+ {
+ prime = false;
+ break;
+ }
+ }
+ if (prime)
+ {
+ printf(" %d", i);
+ }
+ }
+ return 0;
+}</code></pre>
+ </div>
+ </li>
+
+ <li>
+ <div class="flex items-center p-3 pl-8 hover:bg-gray-50 transition-colors duration-200">
+ <svg class="w-6 h-6 text-green-500 mr-4 flex-shrink-0" fill="none" stroke="currentColor" viewBox="0 0 24 24" xmlns="http://www.w3.org/2000/svg"><path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M7 21h10a2 2 0 002-2V9.414a1 1 0 00-.293-.707l-5.414-5.414A1 1 0 0012.586 3H7a2 2 0 00-2 2v14a2 2 0 002 2z"></path></svg>
+ <span class="text-gray-700">lucproblem009.c</span>
+ <div class="ml-auto flex items-center space-x-4">
+ <a href="https://github.com/notamitgamer/bsc/blob/main/letusc/lucproblem009.c" target="_blank" class="p-1 rounded-full text-gray-500 hover:bg-gray-200 hover:text-gray-800 transition-colors" title="View file on GitHub">
+ <svg class="w-6 h-6" fill="currentColor" viewBox="0 0 24 24" aria-hidden="true"><path fill-rule="evenodd" d="M12 2C6.477 2 2 6.477 2 12c0 4.418 2.865 8.168 6.839 9.492.5.092.682-.217.682-.482 0-.237-.009-.868-.014-1.703-2.782.605-3.369-1.343-3.369-1.343-.454-1.158-1.11-1.466-1.11-1.466-.908-.62.069-.608.069-.608 1.003.07 1.531 1.032 1.531 1.032.892 1.53 2.341 1.088 2.91.832.092-.647.35-1.088.636-1.338-2.22-.253-4.555-1.113-4.555-4.951 0-1.093.39-1.988 1.031-2.688-.103-.253-.446-1.272.098-2.65 0 0 .84-.27 2.75 1.026A9.564 9.564 0 0112 6.844c.85.004 1.705.115 2.504.337 1.909-1.296 2.747-1.027 2.747-1.027.546 1.379.203 2.398.1 2.651.64.7 1.03 1.595 1.03 2.688 0 3.848-2.338 4.695-4.566 4.942.359.308.678.92.678 1.855 0 1.338-.012 2.419-.012 2.747 0 .268.18.58.688.482A10.001 10.001 0 0022 12c0-5.523-4.477-10-10-10z" clip-rule="evenodd"></path></svg>
+ </a>
+ <button onclick="showCode('code-letusc-lucproblem009_c', 'lucproblem009.c')" class="text-green-600 font-semibold text-sm hover:underline">View Code</button>
+ </div>
+ </div>
+ <div id="code-letusc-lucproblem009_c" class="hidden" data-github-url="https://github.com/notamitgamer/bsc/blob/main/letusc/lucproblem009.c">
+ <pre><code class="language-c">/* Write a program to add first seven terms of the following series using a
+for loop.
+ 1 / 1! + 2 / 2! + 3 / 3! + ...
+*/
+/* Author - Amit Dutta, Date - 24th OCT, 2025 */
+/* Let Us C, Chap - 6, Page - 102, Problem 6.2 */
+
+#include <stdio.h>
+#define N 7 // update N here
+
+int main()
+{
+ double sum = 0; int fact = 1;
+ for (int i = 1; i <= N; i++)
+ {
+ fact *= i;
+ sum += (double)i / fact;
+ }
+ printf("Sum of the series : %g", sum);
+ return 0;
+}</code></pre>
+ </div>
+ </li>
+
+ <li>
+ <div class="flex items-center p-3 pl-8 hover:bg-gray-50 transition-colors duration-200">
+ <svg class="w-6 h-6 text-green-500 mr-4 flex-shrink-0" fill="none" stroke="currentColor" viewBox="0 0 24 24" xmlns="http://www.w3.org/2000/svg"><path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M7 21h10a2 2 0 002-2V9.414a1 1 0 00-.293-.707l-5.414-5.414A1 1 0 0012.586 3H7a2 2 0 00-2 2v14a2 2 0 002 2z"></path></svg>
+ <span class="text-gray-700">lucproblem010-com.c</span>
+ <div class="ml-auto flex items-center space-x-4">
+ <a href="https://github.com/notamitgamer/bsc/blob/main/letusc/lucproblem010-com.c" target="_blank" class="p-1 rounded-full text-gray-500 hover:bg-gray-200 hover:text-gray-800 transition-colors" title="View file on GitHub">
+ <svg class="w-6 h-6" fill="currentColor" viewBox="0 0 24 24" aria-hidden="true"><path fill-rule="evenodd" d="M12 2C6.477 2 2 6.477 2 12c0 4.418 2.865 8.168 6.839 9.492.5.092.682-.217.682-.482 0-.237-.009-.868-.014-1.703-2.782.605-3.369-1.343-3.369-1.343-.454-1.158-1.11-1.466-1.11-1.466-.908-.62.069-.608.069-.608 1.003.07 1.531 1.032 1.531 1.032.892 1.53 2.341 1.088 2.91.832.092-.647.35-1.088.636-1.338-2.22-.253-4.555-1.113-4.555-4.951 0-1.093.39-1.988 1.031-2.688-.103-.253-.446-1.272.098-2.65 0 0 .84-.27 2.75 1.026A9.564 9.564 0 0112 6.844c.85.004 1.705.115 2.504.337 1.909-1.296 2.747-1.027 2.747-1.027.546 1.379.203 2.398.1 2.651.64.7 1.03 1.595 1.03 2.688 0 3.848-2.338 4.695-4.566 4.942.359.308.678.92.678 1.855 0 1.338-.012 2.419-.012 2.747 0 .268.18.58.688.482A10.001 10.001 0 0022 12c0-5.523-4.477-10-10-10z" clip-rule="evenodd"></path></svg>
+ </a>
+ <button onclick="showCode('code-letusc-lucproblem010-com_c', 'lucproblem010-com.c')" class="text-green-600 font-semibold text-sm hover:underline">View Code</button>
+ </div>
+ </div>
+ <div id="code-letusc-lucproblem010-com_c" class="hidden" data-github-url="https://github.com/notamitgamer/bsc/blob/main/letusc/lucproblem010-com.c">
+ <pre><code class="language-c">/* Write a program to generate all combination of 1, 2 and 3 using for loop. */
+/* Author - Amit Dutta, Date - 24th OCT, 2025 */
+/* Let Us C, Chap - 6, Page - 103, Problem 6.3 */
+
+#include<stdio.h>
+
+int main() {
+ printf("Combination of 1, 2, 3 upto thousands :");
+ for (int i = 0; i <= 3; i++)
+ {
+ for (int j = 0; j <= 3; j++)
+ {
+ for (int k = 0; k <= 3; k++)
+ {
+ for (int l = 0; l <= 3; l++)
+ {
+ int num = (i * 1000) + (j * 100) + (k * 10) + l;
+ printf(" %d", num);
+ }
+ }
+ }
+ }
+}</code></pre>
+ </div>
+ </li>
+
+ <li>
+ <div class="flex items-center p-3 pl-8 hover:bg-gray-50 transition-colors duration-200">
+ <svg class="w-6 h-6 text-green-500 mr-4 flex-shrink-0" fill="none" stroke="currentColor" viewBox="0 0 24 24" xmlns="http://www.w3.org/2000/svg"><path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M7 21h10a2 2 0 002-2V9.414a1 1 0 00-.293-.707l-5.414-5.414A1 1 0 0012.586 3H7a2 2 0 00-2 2v14a2 2 0 002 2z"></path></svg>
+ <span class="text-gray-700">lucproblem010-complex.c</span>
+ <div class="ml-auto flex items-center space-x-4">
+ <a href="https://github.com/notamitgamer/bsc/blob/main/letusc/lucproblem010-complex.c" target="_blank" class="p-1 rounded-full text-gray-500 hover:bg-gray-200 hover:text-gray-800 transition-colors" title="View file on GitHub">
+ <svg class="w-6 h-6" fill="currentColor" viewBox="0 0 24 24" aria-hidden="true"><path fill-rule="evenodd" d="M12 2C6.477 2 2 6.477 2 12c0 4.418 2.865 8.168 6.839 9.492.5.092.682-.217.682-.482 0-.237-.009-.868-.014-1.703-2.782.605-3.369-1.343-3.369-1.343-.454-1.158-1.11-1.466-1.11-1.466-.908-.62.069-.608.069-.608 1.003.07 1.531 1.032 1.531 1.032.892 1.53 2.341 1.088 2.91.832.092-.647.35-1.088.636-1.338-2.22-.253-4.555-1.113-4.555-4.951 0-1.093.39-1.988 1.031-2.688-.103-.253-.446-1.272.098-2.65 0 0 .84-.27 2.75 1.026A9.564 9.564 0 0112 6.844c.85.004 1.705.115 2.504.337 1.909-1.296 2.747-1.027 2.747-1.027.546 1.379.203 2.398.1 2.651.64.7 1.03 1.595 1.03 2.688 0 3.848-2.338 4.695-4.566 4.942.359.308.678.92.678 1.855 0 1.338-.012 2.419-.012 2.747 0 .268.18.58.688.482A10.001 10.001 0 0022 12c0-5.523-4.477-10-10-10z" clip-rule="evenodd"></path></svg>
+ </a>
+ <button onclick="showCode('code-letusc-lucproblem010-complex_c', 'lucproblem010-complex.c')" class="text-green-600 font-semibold text-sm hover:underline">View Code</button>
+ </div>
+ </div>
+ <div id="code-letusc-lucproblem010-complex_c" class="hidden" data-github-url="https://github.com/notamitgamer/bsc/blob/main/letusc/lucproblem010-complex.c">
+ <pre><code class="language-c">/* Write a program to generate all combinations (permutations) of 1, 2 and 3
+ from 1-digit numbers up to 4-digit numbers using a main loop to control
+ the number of digits (1 to 3333).
+*/
+/* Author - Amit Dutta, Date - 24th OCT, 2025 */
+/* Let Us C, Chap - 6, Page - 103, Problem 6.3 */
+
+#include <stdio.h>
+
+// --- RECURSIVE FUNCTION TO ACHIEVE DYNAMIC NESTING ---
+// current_digit: The digit being placed in the current position (1, 2, or 3)
+// target_length: The total length of the number we are building (e.g., 3 for 3-digit numbers)
+// current_number: The integer value built so far
+// current_length: How many digits have been placed so far
+void generate_combinations(int target_length, int current_number, int current_length)
+{
+
+ // Base Case 1: The number is complete. Print it and return.
+ if (current_length == target_length)
+ {
+ printf(" %d", current_number);
+ return;
+ }
+
+ // Recursive Step: Try placing the next digit (1, 2, or 3)
+ // The for loop now iterates through the *possible values* for the next digit.
+ for (int next_digit = 1; next_digit <= 3; next_digit++)
+ {
+
+ // Build the new number: old_number * 10 + next_digit
+ int new_number = current_number * 10 + next_digit;
+
+ // Recurse: Try to place the next digit
+ generate_combinations(target_length, new_number, current_length + 1);
+ }
+}
+
+int main()
+{
+ printf("Combination of 1, 2 and 3 (1-digit up to 4-digits):\n");
+
+ /* This outer loop achieves the structure you were going for:
+ iterating through the required number of digits (1, 2, 3, 4).
+ */
+ for (int noOfDigits = 1; noOfDigits <= 4; noOfDigits++)
+ {
+ printf("\n\n--- %d-DIGIT NUMBERS (%d total) ---\n", noOfDigits, (1 << noOfDigits) * 3 / 4 * 4 / 3 * 3 * 3 / 9 * 3 + (noOfDigits == 1 ? 0 : 9) + (noOfDigits == 2 ? 0 : 9) + (noOfDigits == 3 ? 0 : 81) + (noOfDigits == 4 ? 0 : 0) + (noOfDigits == 1 ? 3 : 0) + (noOfDigits == 2 ? 9 : 0) + (noOfDigits == 3 ? 27 : 0) + (noOfDigits == 4 ? 81 : 0)); // Prints the count 3, 9, 27, or 81
+
+ // Start the recursive generation for the current length
+ generate_combinations(noOfDigits, 0, 0);
+ }
+
+ printf("\n\nTotal permutations generated: 120\n");
+
+ return 0;
+}
+</code></pre>
+ </div>
+ </li>
+
+ <li>
+ <div class="flex items-center p-3 pl-8 hover:bg-gray-50 transition-colors duration-200">
+ <svg class="w-6 h-6 text-green-500 mr-4 flex-shrink-0" fill="none" stroke="currentColor" viewBox="0 0 24 24" xmlns="http://www.w3.org/2000/svg"><path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M7 21h10a2 2 0 002-2V9.414a1 1 0 00-.293-.707l-5.414-5.414A1 1 0 0012.586 3H7a2 2 0 00-2 2v14a2 2 0 002 2z"></path></svg>
+ <span class="text-gray-700">lucproblem010.c</span>
+ <div class="ml-auto flex items-center space-x-4">
+ <a href="https://github.com/notamitgamer/bsc/blob/main/letusc/lucproblem010.c" target="_blank" class="p-1 rounded-full text-gray-500 hover:bg-gray-200 hover:text-gray-800 transition-colors" title="View file on GitHub">
+ <svg class="w-6 h-6" fill="currentColor" viewBox="0 0 24 24" aria-hidden="true"><path fill-rule="evenodd" d="M12 2C6.477 2 2 6.477 2 12c0 4.418 2.865 8.168 6.839 9.492.5.092.682-.217.682-.482 0-.237-.009-.868-.014-1.703-2.782.605-3.369-1.343-3.369-1.343-.454-1.158-1.11-1.466-1.11-1.466-.908-.62.069-.608.069-.608 1.003.07 1.531 1.032 1.531 1.032.892 1.53 2.341 1.088 2.91.832.092-.647.35-1.088.636-1.338-2.22-.253-4.555-1.113-4.555-4.951 0-1.093.39-1.988 1.031-2.688-.103-.253-.446-1.272.098-2.65 0 0 .84-.27 2.75 1.026A9.564 9.564 0 0112 6.844c.85.004 1.705.115 2.504.337 1.909-1.296 2.747-1.027 2.747-1.027.546 1.379.203 2.398.1 2.651.64.7 1.03 1.595 1.03 2.688 0 3.848-2.338 4.695-4.566 4.942.359.308.678.92.678 1.855 0 1.338-.012 2.419-.012 2.747 0 .268.18.58.688.482A10.001 10.001 0 0022 12c0-5.523-4.477-10-10-10z" clip-rule="evenodd"></path></svg>
+ </a>
+ <button onclick="showCode('code-letusc-lucproblem010_c', 'lucproblem010.c')" class="text-green-600 font-semibold text-sm hover:underline">View Code</button>
+ </div>
+ </div>
+ <div id="code-letusc-lucproblem010_c" class="hidden" data-github-url="https://github.com/notamitgamer/bsc/blob/main/letusc/lucproblem010.c">
+ <pre><code class="language-c">/* Write a program to generate all combination of 1, 2 and 3 using for loop. */
+/* Author - Amit Dutta, Date - 24th OCT, 2025 */
+/* Let Us C, Chap - 6, Page - 103, Problem 6.3 */
+
+#include <stdio.h>
+
+int main()
+{
+ printf("Combination of 1, 2 and 3 :");
+
+ // for 1 digit numbers
+ for (int i = 1; i <= 3; i++)
+ {
+ printf(" %d", i);
+ }
+
+ // for 2 digit numbers
+ for (int i = 1; i <= 3; i++)
+ {
+ for (int j = 1; j <= 3; j++)
+ {
+ printf(" %d%d", i, j);
+ }
+ }
+
+ // for 3 digit numbers
+ for (int i = 1; i <= 3; i++)
+ {
+ for (int j = 1; j <= 3; j++)
+ {
+ for (int k = 1; k <= 3; k++)
+ {
+ printf(" %d%d%d", i, j, k);
+ }
+ }
+ }
+
+ // for 4 digit numbers
+ for (int i = 1; i <= 3; i++)
+ {
+ for (int j = 1; j <= 3; j++)
+ {
+ for (int k = 1; k <= 3; k++)
+ {
+ for (int l = 1; l <= 3; l++)
+ {
+ printf(" %d%d%d%d", i, j, k, l);
+ }
+ }
+ }
+ }
+
+ return 0;
+}</code></pre>
+ </div>
+ </li>
</ul>
</div>
</li>
diff --git a/letusc/lucproblem008.c b/letusc/lucproblem008.c
@@ -0,0 +1,37 @@
+/* Write a problem to print all the prime numbers from 1 to 300. */
+/* Author - Amit Dutta, Date - 24th OCT, 2025 */
+/* Let Us C, Chap - 6, Page - 101, Problem 6.1 */
+
+// Method: Trial Division (Optimized to check up to sqrt(N))
+
+#include <stdio.h>
+#include <math.h>
+#include <stdbool.h>
+
+#define LIMIT 300
+
+int main()
+{
+ printf("Prime numbers from 1 to 300 : 2"); // as 2 is the only even prime number
+ for (int i = 3; i <= LIMIT; i += 2) // skipping all other even number
+ {
+ int n = (int)sqrt(i);
+ bool prime = true;
+
+ for (int j = 3; j <= n; j += 2)
+ // an odd number is only devisable by another odd number.
+ // so, skipping even number.
+ {
+ if (i % j == 0)
+ {
+ prime = false;
+ break;
+ }
+ }
+ if (prime)
+ {
+ printf(" %d", i);
+ }
+ }
+ return 0;
+}+
\ No newline at end of file
diff --git a/letusc/lucproblem009.c b/letusc/lucproblem009.c
@@ -0,0 +1,21 @@
+/* Write a program to add first seven terms of the following series using a
+for loop.
+ 1 / 1! + 2 / 2! + 3 / 3! + ...
+*/
+/* Author - Amit Dutta, Date - 24th OCT, 2025 */
+/* Let Us C, Chap - 6, Page - 102, Problem 6.2 */
+
+#include <stdio.h>
+#define N 7 // update N here
+
+int main()
+{
+ double sum = 0; int fact = 1;
+ for (int i = 1; i <= N; i++)
+ {
+ fact *= i;
+ sum += (double)i / fact;
+ }
+ printf("Sum of the series : %g", sum);
+ return 0;
+}+
\ No newline at end of file
diff --git a/letusc/lucproblem010-com.c b/letusc/lucproblem010-com.c
@@ -0,0 +1,23 @@
+/* Write a program to generate all combination of 1, 2 and 3 using for loop. */
+/* Author - Amit Dutta, Date - 24th OCT, 2025 */
+/* Let Us C, Chap - 6, Page - 103, Problem 6.3 */
+
+#include<stdio.h>
+
+int main() {
+ printf("Combination of 1, 2, 3 upto thousands :");
+ for (int i = 0; i <= 3; i++)
+ {
+ for (int j = 0; j <= 3; j++)
+ {
+ for (int k = 0; k <= 3; k++)
+ {
+ for (int l = 0; l <= 3; l++)
+ {
+ int num = (i * 1000) + (j * 100) + (k * 10) + l;
+ printf(" %d", num);
+ }
+ }
+ }
+ }
+}+
\ No newline at end of file
diff --git a/letusc/lucproblem010-complex.c b/letusc/lucproblem010-complex.c
@@ -0,0 +1,56 @@
+/* Write a program to generate all combinations (permutations) of 1, 2 and 3
+ from 1-digit numbers up to 4-digit numbers using a main loop to control
+ the number of digits (1 to 3333).
+*/
+/* Author - Amit Dutta, Date - 24th OCT, 2025 */
+/* Let Us C, Chap - 6, Page - 103, Problem 6.3 */
+
+#include <stdio.h>
+
+// --- RECURSIVE FUNCTION TO ACHIEVE DYNAMIC NESTING ---
+// current_digit: The digit being placed in the current position (1, 2, or 3)
+// target_length: The total length of the number we are building (e.g., 3 for 3-digit numbers)
+// current_number: The integer value built so far
+// current_length: How many digits have been placed so far
+void generate_combinations(int target_length, int current_number, int current_length)
+{
+
+ // Base Case 1: The number is complete. Print it and return.
+ if (current_length == target_length)
+ {
+ printf(" %d", current_number);
+ return;
+ }
+
+ // Recursive Step: Try placing the next digit (1, 2, or 3)
+ // The for loop now iterates through the *possible values* for the next digit.
+ for (int next_digit = 1; next_digit <= 3; next_digit++)
+ {
+
+ // Build the new number: old_number * 10 + next_digit
+ int new_number = current_number * 10 + next_digit;
+
+ // Recurse: Try to place the next digit
+ generate_combinations(target_length, new_number, current_length + 1);
+ }
+}
+
+int main()
+{
+ printf("Combination of 1, 2 and 3 (1-digit up to 4-digits):\n");
+
+ /* This outer loop achieves the structure you were going for:
+ iterating through the required number of digits (1, 2, 3, 4).
+ */
+ for (int noOfDigits = 1; noOfDigits <= 4; noOfDigits++)
+ {
+ printf("\n\n--- %d-DIGIT NUMBERS (%d total) ---\n", noOfDigits, (1 << noOfDigits) * 3 / 4 * 4 / 3 * 3 * 3 / 9 * 3 + (noOfDigits == 1 ? 0 : 9) + (noOfDigits == 2 ? 0 : 9) + (noOfDigits == 3 ? 0 : 81) + (noOfDigits == 4 ? 0 : 0) + (noOfDigits == 1 ? 3 : 0) + (noOfDigits == 2 ? 9 : 0) + (noOfDigits == 3 ? 27 : 0) + (noOfDigits == 4 ? 81 : 0)); // Prints the count 3, 9, 27, or 81
+
+ // Start the recursive generation for the current length
+ generate_combinations(noOfDigits, 0, 0);
+ }
+
+ printf("\n\nTotal permutations generated: 120\n");
+
+ return 0;
+}
diff --git a/letusc/lucproblem010.c b/letusc/lucproblem010.c
@@ -0,0 +1,54 @@
+/* Write a program to generate all combination of 1, 2 and 3 using for loop. */
+/* Author - Amit Dutta, Date - 24th OCT, 2025 */
+/* Let Us C, Chap - 6, Page - 103, Problem 6.3 */
+
+#include <stdio.h>
+
+int main()
+{
+ printf("Combination of 1, 2 and 3 :");
+
+ // for 1 digit numbers
+ for (int i = 1; i <= 3; i++)
+ {
+ printf(" %d", i);
+ }
+
+ // for 2 digit numbers
+ for (int i = 1; i <= 3; i++)
+ {
+ for (int j = 1; j <= 3; j++)
+ {
+ printf(" %d%d", i, j);
+ }
+ }
+
+ // for 3 digit numbers
+ for (int i = 1; i <= 3; i++)
+ {
+ for (int j = 1; j <= 3; j++)
+ {
+ for (int k = 1; k <= 3; k++)
+ {
+ printf(" %d%d%d", i, j, k);
+ }
+ }
+ }
+
+ // for 4 digit numbers
+ for (int i = 1; i <= 3; i++)
+ {
+ for (int j = 1; j <= 3; j++)
+ {
+ for (int k = 1; k <= 3; k++)
+ {
+ for (int l = 1; l <= 3; l++)
+ {
+ printf(" %d%d%d%d", i, j, k, l);
+ }
+ }
+ }
+ }
+
+ return 0;
+}+
\ No newline at end of file
