Equal score substrings

String Prefix Sum

56.7% acceptance

Feb 24, 2026

You are given a string s consisting of lowercase English letters. The score of a string is the sum of the positions of its characters in the alphabet, where 'a' = 1, 'b' = 2, ..., 'z' = 26. Determine whether there exists an index i such that the string can be split into two non-empty substrings s[0..i] and s[(i + 1)..(n - 1)] that have equal scores. Return true if such a split exists, otherwise return false.

Solution

Rust

Time O(n)

Space O(1)

LeetCode

solution.rs

impl Solution {
  pub fn score_balance(s: String) -> bool {
    let chars: Vec<i32> = s.bytes().map(|b| (b - b'a' + 1) as i32).collect();
    let total: i32 = chars.iter().sum();
    let mut prefix = 0i32;
    for i in 0..chars.len() - 1 {
      prefix += chars[i];
      if prefix * 2 == total {
        return true;
      }
    }
    false
  }
}