Contiguous Array LeetCode solution in C++

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class Solution {
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 public:
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  int findMaxLength(vector<int> &nums) {
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    unordered_map<int, int> mp;
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    mp[0] = -1;
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    int sum = 0, longest_subarray = 0;
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    for (int i = 0; i < nums.size(); i++) {
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      sum += nums[i] == 0 ? -1 : 1;
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      if (mp.find(sum) != mp.end()) {
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        if (longest_subarray < i - mp[sum]) {
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          longest_subarray = i - mp[sum];
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        }
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      } else {
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        mp[sum] = i;
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      }
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    }
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    return longest_subarray;
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  }
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};