Question

How to generate all possible permutations of N numbers in C++

Answer 1

#include <iostream>
 
void printArray(int a[], int constant_len) {
    for (int i = 0; i < constant_len; i++)
        std::cout << a[i] << " ";
    std::cout << "\n";
}
   
void heapAlgorithmPermutation(int a[], int len, int constant_len) {
    if (len == 1) {
        printArray(a, constant_len);
        return;
    }
   
    for (int i = 0; i < len; i++) {
        heapAlgorithmPermutation(a, len - 1, constant_len);
  
        if (len % 2 == 1)
            std::swap(a[0], a[len - 1]);
        else
            std::swap(a[i], a[len - 1]);
    }
}
 
int main() {
    int arr[] = {1, 2, 3, 4};
  
    int len = sizeof arr / sizeof arr[0];
  
    heapAlgorithmPermutation(arr, len, len);
  
    return 0;
}
 
 
 
 
/*
run:
 
1 2 3 4 
2 1 3 4 
3 1 2 4 
1 3 2 4 
2 3 1 4 
3 2 1 4 
4 2 3 1 
2 4 3 1 
3 4 2 1 
4 3 2 1 
2 3 4 1 
3 2 4 1 
4 1 3 2 
1 4 3 2 
3 4 1 2 
4 3 1 2 
1 3 4 2 
3 1 4 2 
4 1 2 3 
1 4 2 3 
2 4 1 3 
4 2 1 3 
1 2 4 3 
2 1 4 3 
 
*/

 

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