maximum-size-subarray-sum-equals-k.js

/**
 * 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:
 *
 * Input: nums = [1, -1, 5, -2, 3], k = 3
 * Output: 4
 *
 * Explanation: The subarray [1, -1, 5, -2] sums to 3 and is the longest.
 *
 * Example 2:
 *
 * Input: nums = [-2, -1, 2, 1], k = 1
 * Output: 2
 *
 * Explanation: The subarray [-1, 2] sums to 1 and is the longest.
 *
 * Follow Up:
 * Can you do it in O(n) time?
 */

/**
 * @param {number[]} nums
 * @param {number} k
 * @return {number}
 */
const maxSubArrayLen = (nums, k) => {
  const map = { 0: -1 };

  let len = 0;

  for (let i = 0, sum = 0; i < nums.length; i++) {
    sum += nums[i];

    if (sum - k in map) {
      len = Math.max(len, i - map[sum - k]);
    }

    if (!(sum in map)) {
      map[sum] = i;
    }
  }

  return len;
};

export { maxSubArrayLen };