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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;
    }
};
  • 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;
        }
    }
    
    ############
    
    class Solution {
        public int maxScore(String s) {
            int t = 0;
            if (s.charAt(0) == '0') {
                t++;
            }
            for (int i = 1; i < s.length(); ++i) {
                if (s.charAt(i) == '1') {
                    t++;
                }
            }
            int ans = t;
            for (int i = 1; i < s.length() - 1; ++i) {
                t += s.charAt(i) == '0' ? 1 : -1;
                ans = Math.max(ans, t);
            }
            return ans;
        }
    }
    
  • // 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;
        }
    };
    
  • class Solution:
        def maxScore(self, s: str) -> int:
            ans = t = (s[0] == '0') + s[1:].count('1')
            for i in range(1, len(s) - 1):
                t += 1 if s[i] == '0' else -1
                ans = max(ans, t)
            return ans
    
    
    
  • func maxScore(s string) int {
    	t := 0
    	if s[0] == '0' {
    		t++
    	}
    	n := len(s)
    	for i := 1; i < n; i++ {
    		if s[i] == '1' {
    			t++
    		}
    	}
    	ans := t
    	for i := 1; i < n-1; i++ {
    		if s[i] == '0' {
    			t++
    		} else {
    			t--
    		}
    		ans = max(ans, t)
    	}
    	return ans
    }
    
    func max(a, b int) int {
    	if a > b {
    		return a
    	}
    	return b
    }
    
  • function maxScore(s: string): number {
        const n = s.length;
        let res = 0;
        let score = 0;
        if (s[0] === '0') {
            score++;
        }
        for (let i = 1; i < n; i++) {
            if (s[i] === '1') {
                score++;
            }
        }
        res = Math.max(res, score);
        for (let i = 1; i < n - 1; i++) {
            if (s[i] === '0') {
                score++;
            } else if (s[i] === '1') {
                score--;
            }
            res = Math.max(res, score);
        }
        return res;
    }
    
    
  • impl Solution {
        pub fn max_score(s: String) -> i32 {
            let n = s.len();
            let mut res = 0;
            let mut score = 0;
            let bs = s.as_bytes();
            if bs[0] == b'0' {
                score += 1;
            }
            for i in 1..n {
                if bs[i] == b'1' {
                    score += 1;
                }
            }
            res = res.max(score);
            for i in 1..n - 1 {
                if bs[i] == b'0' {
                    score += 1;
                } else if bs[i] == b'1' {
                    score -= 1;
                }
                res = res.max(score);
            }
            res
        }
    }
    
    

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