Lexicographic rank of a string using STL
You are given a string, find its rank among all its permutations sorted lexicographically.
Examples:
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Input : str[] = "acb" Output : Rank = 2 Input : str[] = "string" Output : Rank = 598 Input : str[] = "cba" Output : Rank = 6
We have already discussed solutions to find Lexicographic rank of string
In this post, we use the STL function “next_permutation ()” to generate all possible permutations of the given string and, as it gives us permutations in lexicographic order, we will put an iterator to find the rank of each string. While iterating when Our permuted string becomes identical to the original input string, we break from the loop and the iterator value for the last iteration is our required result.
// C++ program to print rank of // string using next_permute()#include <bits/stdc++.h>using namespace std; // Function to print rank of string// using next_permute()int findRank(string str){ // store original string string orgStr = str; // Sort the string in lexicographically // ascending order sort(str.begin(), str.end()); // Keep iterating until // we reach equality condition long int i = 1; do { // check for nth iteration if (str == orgStr) break; i++; } while (next_permutation(str.begin(), str.end())); // return iterator value return i;} // Driver codeint main(){ string str = "GEEKS"; cout << findRank(str); return 0;} |
Output:
25
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