1658. Minimum Operations to Reduce X to Zero

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# 題目敘述

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 .

# Example 1

Input: nums = [1,1,4,2,3], x = 5
Output: 2
Explanation: The optimal solution is to remove the last two elements to reduce x to zero.

# Example 2

Input: nums = [5,6,7,8,9], x = 4
Output: -1

# Example 3

Input: nums = [3,2,20,1,1,3], x = 10
Output: 5
Explanation: The optimal solution is to remove the last three elements and the first two elements (5 operations in total) to reduce x to zero.

# 解題思路

# Solution

public class Solution {

    public int minOperations(int[] nums, int x) {

        int total = 0;

        for (int num : nums) {

            total += num;

        }

        int target = total - x;

        int left = 0;

        int n = nums.length;

        int maxWindow = -1;

        int sum = 0;

        for (int right = 0; right < n; right++) {

            sum += nums[right];

            while (sum > target && left <= right) {

                sum -= nums[left];

                left++;

            }

            if (sum == target) {

                maxWindow = Math.max(maxWindow, right - left + 1);

            }

        }

        return maxWindow != -1 ? n - maxWindow : -1;

    }

}