#696 - Count Binary Substrings

Easy • View on LeetCode • View on GitHub

Problem Description

Given a binary string s, return the number of non-empty substrings that have the same number of 0's and 1's, and all the 0's and all the 1's in these substrings are grouped consecutively.

Substrings that occur multiple times are counted the number of times they occur.

Solution

/**
 * @param {string} s
 * @return {number}
 */
var countBinarySubstrings = function(s) {
  let result = 0;

  for (let i = 0, group = [], count = 1, prevCount = 0; i < s.length; i++) {
    if (s[i] === s[i + 1]) {
      count++;
    } else {
      if (prevCount) {
        result += prevCount <= count ? prevCount : count;
      }
      prevCount = count;
      count = 1;
    }
  }

  return result;
};