Keep track of previous indexes after sorting a vector in C++ STL
Prerequisite: vector, vector pair sorting
Given a vector, keep track of the present indexes corresponding to each element and after sorting print element with its previous respective indexes.
Examples:
Input: Arr[] = {2, 5, 3, 7, 1}
Output: {1, 4} {2, 0} {3, 2} {5, 1} {7, 3}
Explanation:
Before sorting [index(element)]: [0(2), 1(5), 2(3), 3(7), 4(1)]
After sorting [previous_index(element)]: [4(1), 0(2), 2(3), 1(5), 3(7)]Input: Arr[] = {4, 5, 10, 8, 3, 11}
Output: {3, 4} {4, 0} {5, 1} {8, 3} {10, 2} {11, 5}
Approach: The idea is to store each element with its present index in a vector pair and then sort all the elements of the vector, Finally, print the elements with its index associated with it.
Below is the implementation of the above approach:
// C++ implementation to keep track// of previous indexes// after sorting a vector #include <bits/stdc++.h>using namespace std; void sortArr(int arr[], int n){ // Vector to store element // with respective present index vector<pair<int, int> > vp; // Inserting element in pair vector // to keep track of previous indexes for (int i = 0; i < n; ++i) { vp.push_back(make_pair(arr[i], i)); } // Sorting pair vector sort(vp.begin(), vp.end()); // Displaying sorted element // with previous indexes // corresponding to each element cout << "Element\t" << "index" << endl; for (int i = 0; i < vp.size(); i++) { cout << vp[i].first << "\t" << vp[i].second << endl; }} // Driver codeint main(){ int arr[] = { 2, 5, 3, 7, 1 }; int n = sizeof(arr) / sizeof(arr[0]); sortArr(arr, n); return 0;} |
Element index 1 4 2 0 3 2 5 1 7 3
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