#1658 - Minimum Operations to Reduce X to Zero

Medium • View on LeetCode • View on GitHub

Array Hash Table Binary Search Prefix Sum Sliding Window

Problem Description

You are given an integer array nums and an integer x. In one operation, you can either remove the leftmost or the rightmost element from the array nums and subtract its value from x. Note that this modifies the array for future operations.

Return the minimum number of operations to reduce x to exactly 0 if it is possible, otherwise, return -1.

Solution

/**
 * @param {number[]} nums
 * @param {number} x
 * @return {number}
 */
var minOperations = function(nums, x) {
  const targetSum = nums.reduce((sum, num) => sum + num, 0) - x;
  if (targetSum < 0) return -1;
  if (targetSum === 0) return nums.length;

  let currentSum = 0;
  let maxLength = -1;
  let left = 0;

  for (let right = 0; right < nums.length; right++) {
    currentSum += nums[right];

    while (currentSum > targetSum && left <= right) {
      currentSum -= nums[left];
      left++;
    }

    if (currentSum === targetSum) {
      maxLength = Math.max(maxLength, right - left + 1);
    }
  }

  return maxLength === -1 ? -1 : nums.length - maxLength;
};