Question

How to rearrange an array and set arr[arr[index]] to index in C++

Answer 1

#include <iostream>

void rearrange_array(int arr[], int size) {
    int tmp[10] = {0};
 
    for (int i = 0; i < size; i++) {
        tmp[arr[i]] = i;
    }
 
    for (int i = 0; i < size; i++) {
        arr[i] = tmp[i];
    }
}
 
int main(void)
{
    int arr[] = { 3, 1, 0, 4, 5, 2 };
    
    // arr[arr[0]] = 3 -> arr[3] = 0
    // arr[arr[1]] = 1 -> arr[1] = 1
    // arr[arr[2]] = 0 -> arr[0] = 2
    // arr[arr[3]] = 4 -> arr[4] = 3
    // arr[arr[4]] = 5 -> arr[5] = 4
    // arr[arr[5]] = 2 -> arr[2] = 5
    
    int size = sizeof(arr) / sizeof(arr[0]);
 
    rearrange_array(arr, size);
 
    for (int i = 0; i < size; i++) {
        std::cout << arr[i] << " ";
    }
}




/*
run:

2 1 5 0 3 4 

*/

 

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