Leetcode 325. Maximum Size Subarray Sum Equals k (Medium) (cpp)

Leetcode 325. Maximum Size Subarray Sum Equals k (Medium) (cpp)

Tag: Hash Table

Difficulty: Medium

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/*325. Maximum Size Subarray Sum Equals k (Medium)Given an array nums and a target value k, find the maximum length of a subarray that sums to k. If there isn't one, return 0 instead.Note:The sum of the entire nums array is guaranteed to fit within the 32-bit signed integer range.Example 1:Given nums = [1, -1, 5, -2, 3], k = 3,return 4. (because the subarray [1, -1, 5, -2] sums to 3 and is the longest)Example 2:Given nums = [-2, -1, 2, 1], k = 1,return 2. (because the subarray [-1, 2] sums to 1 and is the longest)*/class Solution {public:    int maxSubArrayLen(vector<int>& nums, int k) {        if (nums.empty()) {            return 0;        }        int sum = 0, len = 0;        unordered_map<int, int> mapping;        mapping[0] = -1;        for (int i = 0; i < nums.size(); i++) {            sum += nums[i];            if (mapping.find(sum - k) != mapping.end()) {                len = max(len, i - mapping[sum - k]);            }             if (mapping.find(sum) == mapping.end()){                mapping[sum] = i;            }        }        return len;    }};