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#3146
Easy Algorithms

Permutation difference between two strings

Hash Table String
87.8% acceptance
Feb 24, 2026
190
17
You are given two strings s and t such that every character occurs at most once in s and t is a permutation of s. The permutation difference between s and t is defined as the sum of the absolute difference between the index of the occurrence of each character in s and the index of the occurrence of the same character in t. Return the permutation difference between s and t.

Solution

Rust
Time O(n)
Space O(1)
LeetCode
solution.rs 
impl Solution {
  pub fn find_permutation_difference(s: String, t: String) -> i32 {
    let mut pos_s = [0i32; 26];
    let mut pos_t = [0i32; 26];
    for (i, &b) in s.as_bytes().iter().enumerate() {
      pos_s[(b - b'a') as usize] = i as i32;
    }
    for (i, &b) in t.as_bytes().iter().enumerate() {
      pos_t[(b - b'a') as usize] = i as i32;
    }
    s.as_bytes()
      .iter()
      .map(|&b| (pos_s[(b - b'a') as usize] - pos_t[(b - b'a') as usize]).abs())
      .sum()
  }
}