sallyyeng

// time complexity: O(2n) = O(n) = linear;
// space complexity: O(1) contant;

const longestUniformSubstring = function(s) {
  let length = s.length;
  let letter = s[0];
  let startIndex = 0;
  let endIndex = 0;
  let resultIndex = 0;
  let resultLength = 0;