410. Split Array Largest Sum

Problem

Given an array nums which consists of non-negative integers and an integer m, you can split the array into m non-empty continuous subarrays.

Write an algorithm to minimize the largest sum among these m subarrays.

  Example 1:

Input: nums = [7,2,5,10,8], m = 2
Output: 18
Explanation:
There are four ways to split nums into two subarrays.
The best way is to split it into [7,2,5] and [10,8],
where the largest sum among the two subarrays is only 18.

Example 2:

Input: nums = [1,2,3,4,5], m = 2
Output: 9

Example 3:

Input: nums = [1,4,4], m = 3
Output: 4

  Constraints:

• 1 <= nums.length <= 1000

• 0 <= nums[i] <= 10^6

• 1 <= m <= min(50, nums.length)

Solution

/**
 * @param {number[]} nums
 * @param {number} m
 * @return {number}
 */
var splitArray = function(nums, m) {
    function checkIsFeasable (threshold) {
        let count = 1
        let total = 0
        for (const num of nums){
            total += num
            if (total > threshold){
               total = num
                count += 1
                if (count > m){
                    return false   
                }
            }

        }
        return true
    }
    // Binary search template
    let left = Math.max(...nums), right = nums.reduce((all, item) => all+item)
    while(left < right) {
        const mid = left + Math.floor((right-left)/2)
        if(checkIsFeasable(mid)) {
            right = mid
        } else {
            left = mid + 1
        }
    }
    return left
};

Explain:

nope.

Complexity:

• Time complexity : O(n).
• Space complexity : O(n).