Generate All Permutations of Array in DSA C - Build from Scratch

Generate All Permutations of Array

📖 Scenario: You are working on a puzzle game where you need to find all possible orders of a set of unique numbers. This helps the game create different challenges by rearranging the numbers in every possible way.

🎯 Goal: Build a program in C that generates and prints all permutations of a given array of integers.

📋 What You'll Learn

Create an integer array called arr with the exact values 1, 2, 3

Create an integer variable called n that stores the size of arr

Write a function called swap that swaps two integers by their pointers

Write a recursive function called permute that generates all permutations of arr

Print each permutation on a separate line with elements separated by spaces

💡 Why This Matters

🌍 Real World

Generating permutations is useful in games, puzzles, and testing all possible arrangements of items.

💼 Career

Understanding recursion and permutations helps in algorithm design, problem solving, and coding interviews.

1

Create the array and its size

Create an integer array called arr with the exact values 1, 2, 3. Also create an integer variable called n that stores the size of arr.

DSA C

# Create the array arr with values 1, 2, 3
# Create the integer n to store the size of arr

Hint

Use int arr[] = {1, 2, 3}; to create the array and int n = 3; for its size.

2

Write a swap function

Write a function called swap that takes two integer pointers a and b and swaps the values they point to.

DSA C

#include 

int arr[] = {1, 2, 3};
int n = 3;

// Write the swap function below

Hint

Use a temporary variable to hold one value while swapping.

3

Write the recursive permute function

Write a recursive function called permute that takes an integer start. It should generate all permutations of arr by swapping elements starting from index start to n - 1. When start equals n, print the current permutation.

DSA C

#include 

int arr[] = {1, 2, 3};
int n = 3;

void swap(int *a, int *b) {
    int temp = *a;
    *a = *b;
    *b = temp;
}

// Write the permute function below

Hint

Use recursion and swap elements to generate permutations. Remember to swap back after recursive call.

4

Call permute and print all permutations

In the main function, call permute(0) to generate and print all permutations of arr.

DSA C

#include 

int arr[] = {1, 2, 3};
int n = 3;

void swap(int *a, int *b) {
    int temp = *a;
    *a = *b;
    *b = temp;
}

void permute(int start) {
    if (start == n) {
        for (int i = 0; i < n; i++) {
            printf("%d", arr[i]);
            if (i < n - 1) printf(" ");
        }
        printf("\n");
        return;
    }
    for (int i = start; i < n; i++) {
        swap(&arr[start], &arr[i]);
        permute(start + 1);
        swap(&arr[start], &arr[i]);
    }
}

int main() {
    // Call permute with 0 to print all permutations
    
}

Hint

Call permute(0) inside main and return 0.