325: Maximum Size Subarray Sum Equals k

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.

eg : 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)

public int maxSubArrayLen(int[] nums, int k) {
    int sum = 0, max = 0;
    HashMap<Integer, Integer> map = new HashMap<>();
    map.put(0,-1);
    for (int i = 0; i < nums.length; i++) {
      sum = sum + nums[i];
      //if (sum == k) max = i + 1;
      if (map.containsKey(sum - k))
        max = Math.max(max, i - map.get(sum - k));
      if (!map.containsKey(sum)) map.put(sum, i);
    }
    return max;
}