# Lexicographic rank of a string using STL

You are given a string, find its rank among all its permutations sorted lexicographically.

**Examples:**

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 code ` `int` `main() ` `{ ` ` ` `string str = ` `"GEEKS"` `; ` ` ` `cout << findRank(str); ` ` ` `return` `0; ` `} ` |

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Output:

25

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