maxScore.js

/**
Given a string s of zeros and ones, return the maximum score after splitting the string into two non-empty substrings (i.e. left substring and right substring).

The score after splitting a string is the number of zeros in the left substring plus the number of ones in the right substring.

Example 1:
Input: s = "011101"
Output: 5 
Explanation: 
All possible ways of splitting s into two non-empty substrings are:
left = "0" and right = "11101", score = 1 + 4 = 5 
left = "01" and right = "1101", score = 1 + 3 = 4 
left = "011" and right = "101", score = 1 + 2 = 3 
left = "0111" and right = "01", score = 1 + 1 = 2 
left = "01110" and right = "1", score = 2 + 1 = 3

Example 2:
Input: s = "00111"
Output: 5
Explanation: When left = "00" and right = "111", we get the maximum score = 2 + 3 = 5

Example 3:
Input: s = "1111"
Output: 3
 
Constraints:
2 <= s.length <= 500
The string s consists of characters '0' and '1' only.

* @param {string} s
* @return {number}
*/
var maxScore = function (s) {
    let totalOnes = 0;
    for (let ch of s) {
      if (ch === "1") totalOnes++;
    }

    let maxScore = 0;
    let leftZeros = 0;
    let rightOnes = totalOnes;

    for (let i = 0; i < s.length - 1; i++) {
      if (s[i] === "0") {
        leftZeros++;
      } else {
        rightOnes--;
      }

      maxScore = Math.max(maxScore, leftZeros + rightOnes);
    }

    return maxScore;
};