Maximize the confusion of an exam

String Binary Search Sliding Window Prefix Sum

69.7% acceptance

Feb 25, 2026

3079

A teacher is writing a test with 'T' or 'F' questions. Maximize consecutive same answers by changing at most k answers. Return the maximum number of consecutive 'T's or 'F's after at most k operations.

Solution

Rust

Time O(n²)

Space O(1)

LeetCode

solution.rs

impl Solution {
  pub fn max_consecutive_answers(answer_key: String, k: i32) -> i32 {
    let s: Vec<u8> = answer_key.bytes().collect();
    let max_window = |target: u8| -> i32 {
      let mut left = 0;
      let mut count = 0; // count of non-target chars
      let mut best = 0;
      for right in 0..s.len() {
        if s[right] != target { count += 1; }
        while count > k as usize {
          if s[left] != target { count -= 1; }
          left += 1;
        }
        best = best.max(right - left + 1);
      }
      best as i32
    };
    max_window(b'T').max(max_window(b'F'))
  }
}