# 重新排列數組，如果`arr[i]`為`j`，則`arr[j]`變為`i` | 系列 1 > 原文： [https://www.geeksforgeeks.org/rearrange-array-arrj-becomes-arri-j/](https://www.geeksforgeeks.org/rearrange-array-arrj-becomes-arri-j/) 給定大小為 n 的數組，其中所有元素都是不同的，且范圍從 0 到`n-1`，請更改`arr[]`的內容，以便將`arr[i] = j`更改為`arr[j] = i`。 **示例**： ``` Example 1: Input: arr[] = {1, 3, 0, 2}; Output: arr[] = {2, 0, 3, 1}; Explanation for the above output. Since arr[0] is 1, arr[1] is changed to 0 Since arr[1] is 3, arr[3] is changed to 1 Since arr[2] is 0, arr[0] is changed to 2 Since arr[3] is 2, arr[2] is changed to 3 Example 2: Input: arr[] = {2, 0, 1, 4, 5, 3}; Output: arr[] = {1, 2, 0, 5, 3, 4}; Example 3: Input: arr[] = {0, 1, 2, 3}; Output: arr[] = {0, 1, 2, 3}; Example 4: Input: arr[] = {3, 2, 1, 0}; Output: arr[] = {3, 2, 1, 0}; ``` 一種**簡單解決方案**是創建一個臨時數組，并逐個復制“`i`”到“`temp[arr[i]]`”，其中`i`從 0 到`n-1`不等。 以下是上述想法的實現。 ## C++ ```cpp // A simple C++ program to rearrange contents of arr[] // such that arr[j] becomes j if arr[i] is j #include <bits/stdc++.h> using namespace std; // A simple method to rearrange 'arr[0..n-1]' so that 'arr[j]' // becomes 'i' if 'arr[i]' is 'j' void rearrangeNaive(int arr[], int n) { ????// Create an auxiliary array of same size ????int temp[n], i; ????// Store result in temp[] ????for (i = 0; i < n; i++) ????????temp[arr[i]] = i; ????// Copy temp back to arr[] ????for (i = 0; i < n; i++) ????????arr[i] = temp[i]; } // A utility function to print contents of arr[0..n-1] void printArray(int arr[], int n) { ????int i; ????for (i = 0; i < n; i++) ????????cout << ("%d ", arr[i]); ????cout << ("\n"); } // Driver code int main() { ????int arr[] = { 1, 3, 0, 2 }; ????int n = sizeof(arr) / sizeof(arr[0]); ????cout << ("Given array is \n"); ????printArray(arr, n); ????rearrangeNaive(arr, n); ????cout << ("Modified array is \n"); ????printArray(arr, n); ????return 0; } // This code is contributed by Code_Mech ```