Lab-5: Loops in C Programming

// Program to count positive, negative, and zero numbers
#include <stdio.h>

int main() {
    int num, positive = 0, negative = 0, zeros = 0;
    char choice;
    
    printf("=== Number Classification Program ===\n");
    
    do {
        printf("Enter a number: ");
        scanf("%d", &num);
        
        // Classify the number
        if (num > 0) {
            positive++;
            printf("Positive number detected!\n");
        } else if (num < 0) {
            negative++;
            printf("Negative number detected!\n");
        } else {
            zeros++;
            printf("Zero detected!\n");
        }
        
        printf("Do you want to enter another number? (y/n): ");
        scanf(" %c", &choice);
        
    } while (choice == 'y' || choice == 'Y');
    
    // Display results
    printf("\n=== FINAL RESULTS ===\n");
    printf("Total Positive numbers: %d\n", positive);
    printf("Total Negative numbers: %d\n", negative);
    printf("Total Zeros entered: %d\n", zeros);
    printf("Total numbers entered: %d\n", positive + negative + zeros);
    
    return 0;
}

// Program to generate multiplication table
#include <stdio.h>

int main() {
    int num, range;
    
    printf("=== Multiplication Table Generator ===\n");
    printf("Enter the number for multiplication table: ");
    scanf("%d", &num);
    
    printf("Enter the range (how many multiples): ");
    scanf("%d", &range);
    
    printf("\n=== Multiplication Table of %d ===\n", num);
    printf("================================\n");
    
    // Generate multiplication table using for loop
    for (int i = 1; i <= range; i++) {
        printf("%2d * %2d = %3d\n", num, i, num * i);
    }
    
    printf("================================\n");
    
    return 0;
}

// Program for Pattern A: Number Triangle
#include <stdio.h>

int main() {
    int i, j, space, rows;
    int num = 1;

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

    for (i = 1; i <= rows; i++) {
        // Print leading spaces
        for (space = 1; space <= rows - i; space++) {
            printf(" ");
        }
        // Print numbers in each row
        for (j = 1; j <= i; j++) {
            printf("%d ", num);
            num++;
        }
        printf("\n");
    }

    return 0;
}

// Program for Pattern B: Pascal's Triangle
#include <stdio.h>

int main() {
    int rows;
    
    printf("Enter number of rows for Pascal's Triangle: ");
    scanf("%d", &rows);
    
    printf("\nPattern B: Pascal's Triangle\n");
    printf("============================\n");
    
    for (int i = 0; i < rows; i++) {
        int coeff = 1;
        
        // Print spaces for proper alignment
        for (int space = 1; space < rows - i; space++) {
            printf(" ");
        }
        
        // Print Pascal's triangle coefficients
        for (int j = 0; j <= i; j++) {
            if (j == 0 || i == 0) {
                coeff = 1;
            } else {
                coeff = coeff * (i - j + 1) / j;
            }
            printf("%d ", coeff);
        }
        printf("\n");
    }
    
    return 0;
}

// Program to calculate population growth
#include <stdio.h>

int main() {
    double population = 100000.0;  // Initial population
    double growth_rate = 0.10;      // 10% growth rate
    int years = 10;
    
    printf("=== Population Growth Analysis ===\n");
    printf("Initial Population: %.0f\n", population);
    printf("Annual Growth Rate: %.1f%%\n", growth_rate * 100);
    printf("Time Period: %d years\n\n", years);
    
    printf("Year\t\tPopulation\t\tIncrease\n");
    printf("====================================================\n");
    
    // Display initial population
    printf("Start (Year 0)\t%.0f\t\t\t-\n", population);
    
    // Calculate population for each year
    for (int year = 1; year <= years; year++) {
        double previous_population = population;
        population = population * (1 + growth_rate);
        double increase = population - previous_population;
        
        printf("Year %-10d%.0f\t\t\t+%.0f\n", year, population, increase);
    }
    
    printf("====================================================\n");
    printf("Total Growth: %.0f (%.1f%% increase)\n", 
           population - 100000, ((population - 100000) / 100000) * 100);
    
    return 0;
}

// Program to find Ramanujan Numbers
#include <stdio.h>
#include <math.h>

int main() {
    int limit;
    int found = 0;
    
    printf("=== Ramanujan Number Finder ===\n");
    printf("Enter the limit to search for Ramanujan numbers: ");
    scanf("%d", &limit);
    
    printf("\nSearching for Ramanujan numbers up to %d...\n\n", limit);
    
    // Check each number up to the limit
    for (int n = 1; n <= limit; n++) {
        int ways = 0;
        int pairs[10][2];  // Store up to 10 pairs
        
        // Find all ways to express n as sum of two cubes
        for (int i = 1; i * i * i < n; i++) {
            for (int j = i; i * i * i + j * j * j <= n; j++) {
                if (i * i * i + j * j * j == n) {
                    pairs[ways][0] = i;
                    pairs[ways][1] = j;
                    ways++;
                    if (ways >= 10) break; // Prevent overflow
                }
            }
            if (ways >= 10) break;
        }
        
        // If number can be expressed in 2 or more ways, it's Ramanujan
        if (ways >= 2) {
            found++;
            printf("Ramanujan Number #%d: %d\n", found, n);
            
            for (int k = 0; k < ways; k++) {
                int a = pairs[k][0], b = pairs[k][1];
                printf("  %d³ + %d³ = %d + %d = %d\n", 
                       a, b, a*a*a, b*b*b, n);
            }
            printf("\n");
        }
    }
    
    if (found == 0) {
        printf("No Ramanujan numbers found up to %d.\n", limit);
        printf("Try increasing the limit to at least 2000.\n");
    } else {
        printf("Total Ramanujan numbers found: %d\n", found);
    }
    
    return 0;
}