#1758 - Minimum Changes To Make Alternating Binary String

Easy • View on LeetCode • View on GitHub

Problem Description

You are given a string s consisting only of the characters '0' and '1'. In one operation, you can change any '0' to '1' or vice versa.

The string is called alternating if no two adjacent characters are equal. For example, the string "010" is alternating, while the string "0100" is not.

Return the minimum number of operations needed to make s alternating.

Solution

/**
 * @param {string} s
 * @return {number}
 */
var minOperations = function(s) {
  let changesToZeroStart = 0;
  let changesToOneStart = 0;

  for (let i = 0; i < s.length; i++) {
    const expectedZeroStart = i % 2 === 0 ? '0' : '1';
    const expectedOneStart = i % 2 === 0 ? '1' : '0';
    if (s[i] !== expectedZeroStart) changesToZeroStart++;
    if (s[i] !== expectedOneStart) changesToOneStart++;
  }

  return Math.min(changesToZeroStart, changesToOneStart);
};