LeetCode 525. Contiguous Array

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Contiguous Array - LeetCode

Given a binary array, find the maximum length of a contiguous subarray with equal number of 0 and 1.

Example 1:

Input: [0,1]
Output: 2
Explanation: [0, 1] is the longest contiguous subarray with equal number of 0 and 1.

Example 2:

Input: [0,1,0]
Output: 2
Explanation: [0, 1] (or [1, 0]) is a longest contiguous subarray with equal number of 0 and 1.

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0记成-1。变成找和为0

class Solution {
public:
    int findMaxLength(vector<int>& nums) {
        // 哈希表记录 上一个前缀和等于s的区间 的初始下标
        unordered_map<int, int> hash;
        hash[0] = -1;
        int res = 0, s = 0;
        for (int i = 0; i < nums.size(); i ++ ){
            s += nums[i] ? 1 : -1;
            if(hash.count(s)) res = max(res, i - hash[s]);
            else hash[s] = i;
        }
        return res;
    }
};