commit fc81bc5579916f4d79333853a247b7483b4cea7c
parent 045f35702c1246143b303f28ed6334e795f12646
Author: Amit Dutta <amitdutta4255@gmail.com>
Date: Wed, 1 Oct 2025 18:45:55 +0530
NEW_COMMIT
Diffstat:
9 files changed, 219 insertions(+), 0 deletions(-)
diff --git a/Letusc-exercises/luc015.c b/Letusc-exercises/luc015.c
@@ -0,0 +1,26 @@
+/* Given three points (x1, y1), (x2, y2), and (x3, y3),
+write a program to check if the three poins fall on one straight line. */
+/* Author - Amit Dutta, Date - 1st OCT, 2025 */
+/* Let Us C, Chap- 3, Page - 53, Qn No.: f(f) */
+
+#include <stdio.h>
+#include <math.h>
+#define EPSILON 0.0001
+// Define a small tolerance value (EPSILON) for safe floating-point comparison
+// This is critical because of minor rounding errors in computer arithmetic.
+int main()
+{
+ double x1, x2, x3, y1, y2, y3, area;
+ printf("Enter the point A(x1, y1) : ");
+ scanf("%lf %lf", &x1, &y1);
+ printf("Enter the point B(x2, y2) : ");
+ scanf("%lf %lf", &x2, &y2);
+ printf("Enter the point C(x3, y3) : ");
+ scanf("%lf %lf", &x3, &y3);
+ area = 0.5 * ((x1 * (y2 - y3)) + (x2 * (y3 - y1)) + (x3 * (y1 - y2)));
+ if (fabs(area) < EPSILON) // abs() for integer, fabs() for float, double
+ printf("\nA(%g, %g), B(%g, %g) and C(%g, %g) points fall on one straight line.", x1, y1, x2, y2, x3, y3);
+ else
+ printf("\nA(%g, %g), B(%g, %g) and C(%g, %g) points doesn't fall on one straight line.", x1, y1, x2, y2, x3, y3);
+ return 0;
+}+
\ No newline at end of file
diff --git a/Letusc-exercises/luc015.exe b/Letusc-exercises/luc015.exe
Binary files differ.
diff --git a/Letusc-exercises/luc016.c b/Letusc-exercises/luc016.c
@@ -0,0 +1,42 @@
+/* Given the coordiantes (x, y) of center of a circle and its radius,
+write a program that will determine whether a point lies inside the circle,
+on the circle or outside the circle. (Hint : Use sqrt() and pow() functions.) */
+/* Author - Amit Dutta, Date - 1st OCT, 2025 */
+/* Let Us C, Chap- 3, Page - 53, Qn No.: f(g) */
+
+#include <stdio.h>
+#include <math.h>
+// Define a small tolerance value (EPSILON) for reliable floating-point comparison
+#define EPSILON 0.0001
+
+int main()
+{
+ double h, k;
+ double R;
+ double x, y;
+ double distance_sq;
+ printf("Enter the center coordinates (h, k) : ");
+ scanf("%lf %lf", &h, &k);
+ printf("Enter the radius (R) : ");
+ scanf("%lf", &R);
+ printf("Enter the point P coordinates (x, y) : ");
+ scanf("%lf %lf", &x, &y);
+ distance_sq = pow(x - h, 2) + pow(y - k, 2);
+ double radius_sq = R * R;
+ // Case 1: On the circle (D^2 = R^2) - Use EPSILON for safety!
+ if (fabs(distance_sq - radius_sq) < EPSILON)
+ {
+ printf("The point P(%g, %g) lies ON THE CIRCLE.\n", x, y);
+ }
+ // Case 2: Inside the circle (D^2 < R^2)
+ else if (distance_sq < radius_sq)
+ {
+ printf("The point P(%g, %g) lies INSIDE THE CIRCLE.\n", x, y);
+ }
+ // Case 3: Outside the circle (D^2 > R^2)
+ else
+ {
+ printf("The point P(%g, %g) lies OUTSIDE THE CIRCLE.\n", x, y);
+ }
+ return 0;
+}+
\ No newline at end of file
diff --git a/Letusc-exercises/luc016.exe b/Letusc-exercises/luc016.exe
Binary files differ.
diff --git a/Letusc-exercises/luc017.c b/Letusc-exercises/luc017.c
@@ -0,0 +1,23 @@
+/* Given a point (x, y), write a program to find out if it lies on X-axis, Y-axis or origin. */
+/* Author - Amit Dutta, Date - 1st OCT, 2025 */
+/* Let Us C, Chap- 3, Page - 53, Qn No.: f(h) */
+
+#include <stdio.h>
+#include <math.h>
+#define EPSILON 0.00001
+
+int main()
+{
+ double x, y;
+ printf("Enter the point P(x, y) : ");
+ scanf("%lf %lf", &x, &y);
+ if (fabs(x) < EPSILON && fabs(y) < EPSILON)
+ printf("\nPoint P(%g, %g) lies on the origin.", x, y);
+ else if (fabs(x) < EPSILON)
+ printf("\nPoint P(%g, %g) lies on the Y-Axis.", x, y);
+ else if (fabs(y) < EPSILON)
+ printf("\nPoint P(%G, %g) lies on the X-Axis.", x, y);
+ else
+ printf("\nThe point P(%g, %g) lies in a QUADRANT (not on an axis or the origin).", x, y);
+ return 0;
+}+
\ No newline at end of file
diff --git a/Letusc-exercises/luc017.exe b/Letusc-exercises/luc017.exe
Binary files differ.
diff --git a/Letusc-exercises/luc018-logic.c b/Letusc-exercises/luc018-logic.c
@@ -0,0 +1,87 @@
+/* According to Gregorian calender, it was Monday on the date 01/01/01.
+Write a program to find out what is the day on 1st January of any input year. */
+/* Author - Amit Dutta, Date - 1st OCT, 2025 */
+/* Let Us C, Chap- 3, Page - 53, Qn No.: f(i) */
+
+#include <stdio.h>
+
+/**
+ * @brief Determines if a given year is a leap year.
+ * * The rule: A year is a leap year if it is divisible by 4, UNLESS it is
+ * divisible by 100 but NOT by 400.
+ * * @param year The year to check.
+ * @return 1 if it is a leap year, 0 otherwise.
+ */
+int is_leap(int year) {
+ // Check if divisible by 400 OR (divisible by 4 AND not divisible by 100)
+ if ((year % 400 == 0) || (year % 4 == 0 && year % 100 != 0)) {
+ return 1;
+ }
+ return 0;
+}
+
+/**
+ * @brief Calculates the day of the week for January 1st of the given year.
+ * * The base date is 01/01/01, which was a Monday (index 1).
+ * * Day Mapping: 0:Sunday, 1:Monday, 2:Tuesday, 3:Wednesday, 4:Thursday, 5:Friday, 6:Saturday
+ */
+int main() {
+ long long year; // Use long long for year input if years far in the future/past are tested
+ int i;
+ long long total_days = 0;
+ int day_index;
+
+ // Day names array for output
+ const char *day_names[] = {"Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday"};
+
+ printf("Enter the year (e.g., 2025): ");
+ if (scanf("%lld", &year) != 1 || year < 1) {
+ printf("Invalid year input. Please enter a positive integer year (>= 1).\n");
+ return 1;
+ }
+
+ // --- Core Logic: Calculate Total Days ---
+
+ // We only need to consider the years that have *passed* before the target year.
+ // So, we count days from the end of year 0 up to the end of year (year - 1).
+ int years_passed = year - 1;
+
+ // 1. Calculate the number of leap days up to the end of year (year - 1)
+ // Formula based on Gregorian calendar rules for years Y-1:
+ // (Y-1)/4 - (Y-1)/100 + (Y-1)/400
+ long long leap_years = years_passed / 4 - years_passed / 100 + years_passed / 400;
+
+ // 2. Total days = (Number of years * 365) + (Number of leap years)
+ // Note: The loop method (below) is more intuitive but the formula is faster.
+ // We will use the direct formula for efficiency.
+ total_days = years_passed * 365 + leap_years;
+
+ // --- Alternate Loop Method (for conceptual simplicity) ---
+ /*
+ for (i = 1; i < year; i++) {
+ total_days += 365;
+ if (is_leap(i)) {
+ total_days += 1; // Add 1 for the leap day
+ }
+ }
+ */
+
+ // --- Determine the Day of the Week ---
+
+ // Since 01/01/01 was Monday (index 1), we use the following setup:
+ // Index 1 corresponds to Monday.
+ // The calculation gives the number of days *past* the Monday start (01/01/01).
+ // The modulo operation gives the remainder (0-6).
+
+ // 0 days elapsed (Year 1): total_days=0. (0 + 1) % 7 = 1 (Monday). Correct.
+ // 365 days elapsed (Year 2): total_days=365. (365 + 1) % 7 = 2 (Tuesday). Correct. (365 mod 7 = 1, 1+1 = 2)
+
+ day_index = (total_days + 1) % 7;
+
+ // Correct the Day Index to match the array (0:Sun, 1:Mon, ..., 6:Sat)
+ // The +1 adjusts for the Monday starting point (index 1).
+
+ printf("\nOn January 1st, %lld, the day was: **%s**.\n", year, day_names[day_index]);
+
+ return 0;
+}+
\ No newline at end of file
diff --git a/Letusc-exercises/luc018.c b/Letusc-exercises/luc018.c
@@ -0,0 +1,36 @@
+/* According to Gregorian calender, it was Monday on the date 01/01/01.
+if any year is input through the keyboard write a program to find out
+what is the day on 1st January of this year. */
+/* Author - Amit Dutta, Date - 1st OCT, 2025 */
+/* Let Us C, Chap- 3, Page - 53, Qn No.: f(i) */
+
+#include <stdio.h>
+
+int is_leap(int year) {
+ if ((year % 400 == 0) || (year % 4 == 0 && year % 100 != 0)) {
+ return 1;
+ }
+ return 0;
+}
+
+int main() {
+ long long year; // long long for year input if years far in the future/past are tested
+ int i;
+ long long total_days = 0;
+ int day_index;
+
+ // Day names array for output
+ const char *day_names[] = {"Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday"};
+
+ printf("Enter the year (e.g., 2025): ");
+ if (scanf("%lld", &year) != 1 || year < 1) {
+ printf("Invalid year input. Please enter a positive integer year (>= 1).\n");
+ return 1;
+ }
+ int years_passed = year - 1;
+ long long leap_years = years_passed / 4 - years_passed / 100 + years_passed / 400;
+ total_days = years_passed * 365 + leap_years;
+ day_index = (total_days + 1) % 7;
+ printf("\nOn January 1st, %lld, the day was: %s.\n", year, day_names[day_index]);
+ return 0;
+}+
\ No newline at end of file
diff --git a/Letusc-exercises/luc018.exe b/Letusc-exercises/luc018.exe
Binary files differ.
