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| 1 | +// C++ program to find minimum number of swaps required to sort an array |
| 2 | +#include <algorithm> |
| 3 | +#include <iostream> |
| 4 | +#include <utility> |
| 5 | +#include <vector> |
| 6 | + |
| 7 | +// Function returns the minimum number of swaps |
| 8 | +// required to sort the array |
| 9 | +int minSwaps(int arr[], int n) { |
| 10 | + // Create an array of pairs where first |
| 11 | + // element is array element and second element |
| 12 | + // is position of first element |
| 13 | + std::pair<int, int> arrPos[n]; |
| 14 | + for (int i = 0; i < n; i++) { |
| 15 | + arrPos[i].first = arr[i]; |
| 16 | + arrPos[i].second = i; |
| 17 | + } |
| 18 | + |
| 19 | + // Sort the array by array element values to |
| 20 | + // get right position of every element as second |
| 21 | + // element of pair. |
| 22 | + std::sort(arrPos, arrPos + n); |
| 23 | + |
| 24 | + // To keep track of visited elements. Initialize |
| 25 | + // all elements as not visited or false. |
| 26 | + std::vector<bool> vis(n, false); |
| 27 | + |
| 28 | + // Initialize result |
| 29 | + int ans = 0; |
| 30 | + |
| 31 | + // Traverse array elements |
| 32 | + for (int i = 0; i < n; i++) { |
| 33 | + // already swapped and corrected or |
| 34 | + // already present at correct pos |
| 35 | + if (vis[i] || arrPos[i].second == i) |
| 36 | + continue; |
| 37 | + |
| 38 | + // find out the number of node in |
| 39 | + // this cycle and add in ans |
| 40 | + int cycle_size = 0; |
| 41 | + int j = i; |
| 42 | + while (!vis[j]) { |
| 43 | + vis[j] = 1; |
| 44 | + |
| 45 | + // move to next node |
| 46 | + j = arrPos[j].second; |
| 47 | + cycle_size++; |
| 48 | + } |
| 49 | + |
| 50 | + // Update answer by adding current cycle. |
| 51 | + if (cycle_size > 0) { |
| 52 | + ans += (cycle_size - 1); |
| 53 | + } |
| 54 | + } |
| 55 | + |
| 56 | + // Return result |
| 57 | + return ans; |
| 58 | +} |
| 59 | + |
| 60 | +// program to test |
| 61 | +int main() { |
| 62 | + int arr[] = {6, 7, 8, 1, 2, 3, 9, 12}; |
| 63 | + int n = (sizeof(arr) / sizeof(int)); |
| 64 | + std::cout << minSwaps(arr, n); |
| 65 | + return 0; |
| 66 | +} |
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