Given a binary array nums, return the maximum length of a contiguous subarray with an equal number of 0 and 1.
Example 1:
Input: nums = [0,1] Output: 2 Explanation: [0, 1] is the longest contiguous subarray with an equal number of 0 and 1.
Example 2:
Input: nums = [0,1,0] Output: 2 Explanation: [0, 1] (or [1, 0]) is a longest contiguous subarray with equal number of 0 and 1.
Constraints:
1 <= nums.length <= 105nums[i] is either 0 or 1.class Solution {
public:
int findMaxLength(vector<int>& a) {
int f=0, ans=0;
unordered_map<int,int>mp;
mp[0] = -1;
for(int i=0; i<a.size(); i++){
f += a[i]==1 ? 1 : -1;
if(mp.find(f) == mp.end())
mp[ f ] = i;
else
ans = max(ans, i - mp[f] );
}
return ans;
}
};