day-13.cpp

/*
Question: 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.
Note: The length of the given binary array will not exceed 50,000.
*/

class Solution {
   public:
    int findMaxLength(vector<int>& nums) {
        unordered_map<int, int> hashMap;
        hashMap[0] = -1;
        int ans = 0;
        int curr = 0;
        for (int i = 0; i < nums.size(); i++) {
            if (nums[i] == 0) {
                curr -= 1;
            } else {
                curr += 1;
            }

            if (hashMap.find(curr) != hashMap.end()) {
                ans = max(ans, i - hashMap[curr]);
            } else {
                hashMap[curr] = i;
            }
        }

        return ans;
    }
};