Loops — 5 More Examples

#include <stdio.h>

int main() {
    int n;

    printf("How many Fibonacci numbers? ");
    scanf("%d", &n);

    int a = 0, b = 1, next;

    printf("Fibonacci Series: ");

    for (int i = 1; i <= n; i++) {
        printf("%d ", a);
        next = a + b;   // next = sum of previous two
        a = b;          // shift: a becomes b
        b = next;       // b becomes the new number
    }
    printf("\n");

    // Also check if input n is in the series
    int x, p = 0, q = 1;
    printf("Enter a number to check if it is Fibonacci: ");
    scanf("%d", &x);

    while (p < x) { int t = p + q; p = q; q = t; }

    if (p == x || x == 0)
        printf("%d IS a Fibonacci number!\n", x);
    else
        printf("%d is NOT a Fibonacci number.\n", x);

    return 0;
}

#include <stdio.h>

int main() {
    int n, original, reversed = 0, digit;

    printf("Enter a number: ");
    scanf("%d", &n);
    original = n;

    while (n != 0) {
        digit    = n % 10;           // extract last digit
        reversed = reversed * 10 + digit; // append to reversed
        n        = n / 10;           // remove last digit
    }

    printf("Original : %d\n", original);
    printf("Reversed : %d\n", reversed);

    if (original == reversed)
        printf("%d is a PALINDROME number!\n", original);
    else
        printf("%d is NOT a palindrome.\n", original);

    return 0;
}

#include <stdio.h>
#include <string.h>

int main() {
    char str[100];
    int  vowels = 0, consonants = 0;

    printf("Enter a word or sentence: ");
    fgets(str, sizeof(str), stdin);  // reads full line

    for (int i = 0; i < strlen(str); i++) {
        char c = str[i];

        // Skip spaces and newline
        if (c == ' ' || c == '\n') continue;

        // Check if vowel (upper or lower case)
        if (c=='a'||c=='e'||c=='i'||c=='o'||c=='u'||
            c=='A'||c=='E'||c=='I'||c=='O'||c=='U') {
            vowels++;
        } else if ((c>='a'&&c<='z')||(c>='A'&&c<='Z')) {
            consonants++;
        }
    }

    printf("Vowels     : %d\n", vowels);
    printf("Consonants : %d\n", consonants);
    printf("Total chars: %d\n", vowels + consonants);

    return 0;
}

#include <stdio.h>

int main() {
    float principal, rate, balance;
    int   years;

    printf("Enter principal amount (Rs): ");
    scanf("%f", &principal);

    printf("Enter annual interest rate (%%): ");
    scanf("%f", &rate);

    printf("Enter number of years: ");
    scanf("%d", &years);

    balance = principal;

    printf("\n%-6s  %-12s  %-12s\n",
           "Year", "Interest", "Balance");
    printf("--------------------------------\n");

    for (int y = 1; y <= years; y++) {
        float interest = balance * rate / 100;
        balance += interest;
        printf("%-6d  Rs %-9.2f  Rs %.2f\n",
               y, interest, balance);
    }

    printf("--------------------------------\n");
    printf("Final balance : Rs %.2f\n", balance);
    printf("Total earned  : Rs %.2f\n", balance - principal);

    return 0;
}

#include <stdio.h>

int main() {
    int secret = 42;    // the number to guess
    int guess, attempts = 0;

    printf("=== NUMBER GUESSING GAME ===\n");
    printf("Guess the number between 1 and 100!\n\n");

    do {
        printf("Your guess: ");
        scanf("%d", &guess);
        attempts++;

        if      (guess < secret) printf("📈 Too low!  Try higher.\n");
        else if (guess > secret) printf("📉 Too high! Try lower.\n");
        else                     printf("🎉 Correct!\n");

    } while (guess != secret);

    printf("\n--- RESULT ---\n");
    printf("You guessed %d in %d attempt(s).\n", secret, attempts);

    if      (attempts == 1)  printf("🏆 Perfect! First try!\n");
    else if (attempts <= 5)  printf("⭐ Excellent! Very few tries!\n");
    else if (attempts <= 10) printf("👍 Good effort!\n");
    else                      printf("😅 Keep practising!\n");

    return 0;
}