Leetcode #1422: Maximum Score After Splitting a String
In this guide, we solve Leetcode #1422 Maximum Score After Splitting a String in Python and focus on the core idea that makes the solution efficient.
You will see the intuition, the step-by-step method, and a clean Python implementation you can use in interviews.
Problem Statement
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).
Quick Facts
- Difficulty: Easy
- Premium: No
- Tags: String, Prefix Sum
Intuition
Range queries become simple once we precompute cumulative sums.
We can transform subarray conditions into prefix comparisons.
Approach
Compute prefix sums and use a map to find matching prefixes.
This avoids nested loops while keeping the logic clear.
Steps:
- Compute prefix sums.
- Use a map to find valid ranges.
- Update the answer.
Example
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
Python Solution
class Solution:
def maxScore(self, s: str) -> int:
l, r = 0, s.count("1")
ans = 0
for x in s[:-1]:
l += int(x) ^ 1
r -= int(x)
ans = max(ans, l + r)
return ans
Complexity
The time complexity is , where is the length of the string . The space complexity is .
Edge Cases and Pitfalls
Watch for boundary values, empty inputs, and duplicate values where applicable. If the problem involves ordering or constraints, confirm the invariant is preserved at every step.
Summary
This Python solution focuses on the essential structure of the problem and keeps the implementation interview-friendly while meeting the constraints.