LeetCode: Maximum Size Subarray Sum Equals k

LeetCode: 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.

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)

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public class Solution {
    public int maxSubArrayLen(int[] nums, int k) {
        if (nums == null || nums.length == 0) {
            return 0;
        }

        int size = nums.length;
        Map<Integer, Integer> map = new HashMap<>();

        int sum = 0;
        int max = 0;
        for (int i = 0; i < size; i++) {
            int n = nums[i];
            sum += n;
            if (sum == k) {
                max = Math.max(max, i+1);
            }
            if (!map.containsKey(sum)) {
                map.put(sum, i);
            }

            int remain =sum-k;
            if (map.containsKey(remain)) {
                max = Math.max(max, i - map.get(remain));
            }
        }
        return max;
    }
}