525_Contiguous_Array

class Solution {
public:
    int findMaxLength(vector<int>& nums) {
        int current_sum = 0, result = 0;
        for (int start = 0; start < nums.size(); ++start){
            current_sum = 0;
            for (int end = start; end < nums.size(); ++end){
                current_sum += nums[end] * 2;
                if (end - start + 1 == current_sum) result = max(current_sum, result);
            }
        }
        return result;
    }
};

class Solution {
public:
    int findMaxLength(vector<int>& nums) {
        int count = 0, maxlength = 0;
        unordered_map<int, int> hashmap;
        hashmap.insert(make_pair(0, -1));
        for (int i = 0; i < nums.size(); ++i){
            count += (nums[i] == 1) ? 1 : -1;
            if (hashmap.count(count) == 0) 
                hashmap.insert(make_pair(count, i));
            else
                maxlength = max(maxlength, i - hashmap[count]);
        }
        return maxlength;
    }
};