Essential C Programming Examples and Algorithms

Leap Year

#include <stdio.h>
int main() {
    int y;
    scanf("%d", &y);
    if ((y % 4 == 0 && y % 100 != 0) || y % 400 == 0)
        printf("Leap Year");
    else
        printf("Not Leap Year");
    return 0;
}

Simple Calculator Using Switch

#include <stdio.h>
int main() {
    char op;
    float a, b;
    scanf(" %c %f %f", &op, &a, &b);
    switch (op) {
        case '+': printf("%.2f", a + b); break;
        case '-': printf("%.2f", a - b); break;
        case '*': printf("%.2f", a * b); break;
        case '/':
            if (b != 0)
                printf("%.2f", a / b);
            else
                printf("Error");
            break;
        default: printf("Invalid Operator");
    }
    return 0;
}

Sum Up to N

#include <stdio.h>
int main() {
    int n, i, sum = 0;
    scanf("%d", &n);
    for (i = 1; i <= n; i++)
        sum += i;
    printf("%d", sum);
    return 0;
}

Prime Number Check

#include <stdio.h>
int main() {
    int n, i, flag = 1;
    scanf("%d", &n);
    if (n <= 1)
        flag = 0;
    for (i = 2; i <= n / 2; i++) {
        if (n % i == 0) {
            flag = 0;
            break;
        }
    }
    if (flag)
        printf("Prime");
    else
        printf("Not Prime");
    return 0;
}

Fibonacci Series

#include <stdio.h>
int main() {
    int n, a = 0, b = 1, c, i;
    scanf("%d", &n);
    for (i = 1; i <= n; i++) {
        printf("%d ", a);
        c = a + b;
        a = b;
        b = c;
    }
    return 0;
}

Armstrong Number

#include <stdio.h>
int main() {
    int n, temp, d, sum = 0;
    scanf("%d", &n);
    temp = n;
    while (temp > 0) {
        d = temp % 10;
        sum += d * d * d;
        temp /= 10;
    }
    if (sum == n)
        printf("Armstrong");
    else
        printf("Not Armstrong");
    return 0;
}

Bubble Sort

#include <stdio.h>
int main() {
    int a[50], n, i, j, temp;
    scanf("%d", &n);
    for (i = 0; i < n; i++)
        scanf("%d", &a[i]);
    for (i = 0; i < n - 1; i++) {
        for (j = 0; j < n - i - 1; j++) {
            if (a[j] > a[j + 1]) {
                temp = a[j];
                a[j] = a[j + 1];
                a[j + 1] = temp;
            }
        }
    }
    for (i = 0; i < n; i++)
        printf("%d ", a[i]);
    return 0;
}

Palindrome

#include <stdio.h>
int rev(int n) {
    int r = 0;
    while (n > 0) {
        r = r * 10 + n % 10;
        n /= 10;
    }
    return r;
}
int main() {
    int n;
    scanf("%d", &n);
    if (n == rev(n))
        printf("Palindrome");
    else
        printf("Not Palindrome");
    return 0;
}

Print an Array Using Function

#include <stdio.h>
void print(int a[], int n) {
    int i;
    for (i = 0; i < n; i++)
        printf("%d ", a[i]);
}
int main() {
    int a[50], n, i;
    scanf("%d", &n);
    for (i = 0; i < n; i++)
        scanf("%d", &a[i]);
    print(a, n);
    return 0;
}

Reverse String Without Library

#include <stdio.h>
int main() {
    char s[100];
    int i, len = 0;
    fgets(s, 100, stdin);
    while (s[len] != '\0' && s[len] != '\n')
        len++;
    for (i = len - 1; i >= 0; i--)
        printf("%c", s[i]);
    return 0;
}

Frequency of a Character

#include <stdio.h>
int main() {
    char s[100], c;
    int i, count = 0;
    fgets(s, 100, stdin);
    scanf("%c", &c);
    for (i = 0; s[i] != '\0'; i++) {
        if (s[i] == c)
            count++;
    }
    printf("%d", count);
    return 0;
}