Formatted question description: https://leetcode.ca/all/1422.html

1422. Maximum Score After Splitting a String (Easy)

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.

Related Topics:
String

Solution 1.

zero and one are the counts of 0s in left and 1s in right.

First compute the count of all 1s as one. Then for each i in range [0, N - 2], increment zero if s[i] == '0' and decrement one if s[i] == '1'. The maximum zero + one is the result.

// OJ: https://leetcode.com/problems/maximum-score-after-splitting-a-string

// Time: O(N)
// Space: O(1)
class Solution {
public:
    int maxScore(string s) {
        int one = 0, zero = 0, ans = 0;
        for (char c : s) one += c == '1';
        for (int i = 0; i < s.size() - 1; ++i) {
            char c  = s[i];
            zero += c == '0';
            one -= c == '1';
            ans = max(ans, zero + one);
        }
        return ans;
    }
};

Java

class Solution {
    public int maxScore(String s) {
        int length = s.length();
        int ones = 0;
        for (int i = 0; i < length; i++) {
            char c = s.charAt(i);
            if (c == '1')
                ones++;
        }
        int maxScore = 0;
        int leftZeros = 0, rightOnes = ones;
        for (int i = 1; i < length; i++) {
            char lastC = s.charAt(i - 1);
            if (lastC == '0')
                leftZeros++;
            else
                rightOnes--;
            int score = leftZeros + rightOnes;
            maxScore = Math.max(maxScore, score);
        }
        return maxScore;
    }
}

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