Take K of Each Character From Left and Right - Sliding Window [JS]

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Description 

Solution: Sliding Window

Instead of taking characters on the left and right side, try to take the maximum window in the center (the part we will not be taking).
Maintain a sliding window of characters where each character count does not exceed count[i] - k.

  • Keep moving the right pointer forward.
  • When the character count in the window exceeds count[i] - k, move the left pointer up.

Time Complexity: O(n) 88ms
Space Complexity: O(1) 44.6MB

var takeCharacters = function(s, k) {
  if (k === 0) return 0;
  let n = s.length, count = Array(3).fill(0);
  for (let i = 0; i < n; i++) {
    let charcode = s.charCodeAt(i) - 97;
    count[charcode]++;
  }
  for (let i = 0; i < 3; i++) {
    if (count[i] < k) return -1; // not enough characters in the entire string
  }
  
  let currCount = Array(3).fill(0), ans = n;
  for (let j = 0, i = 0; j < n; j++) {
    let charcode = s.charCodeAt(j) - 97;
    currCount[charcode]++;
    while (currCount[charcode] > count[charcode] - k) { // window contains more than count[charcode] - k of a character, move left pointer up
      currCount[s.charCodeAt(i) - 97]--;
      i++;
    }
    let windowSize = j - i + 1;
    ans = Math.min(ans, n - windowSize);
  }
  return ans;
};
Location: Auckland, New Zealand

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