MinimumValueToGetPositiveStepByStepSum.php

<?php

namespace App;

/**
 * Minimum Value to Get Positive Step by Step Sum
 *
 * Given an array of integers nums, you start with an initial positive value startValue.
 * In each iteration, you calculate the step by step sum of startValue plus elements in nums (from left to right).
 * Return the minimum positive value of startValue such that the step by step sum is never less than 1.
 *
 * Example 1:
 * Input: nums = [-3,2,-3,4,2]
 * Output: 5
 * Explanation: If you choose startValue = 4, in the third iteration your step by step sum is less than 1.
 * step by step sum
 * startValue = 4 | startValue = 5 | nums
 * (4 -3 ) = 1  | (5 -3 ) = 2    |  -3
 * (1 +2 ) = 3  | (2 +2 ) = 4    |   2
 * (3 -3 ) = 0  | (4 -3 ) = 1    |  -3
 * (0 +4 ) = 4  | (1 +4 ) = 5    |   4
 * (4 +2 ) = 6  | (5 +2 ) = 7    |   2
 *
 * Example 2:
 * Input: nums = [1,2]
 * Output: 1
 * Explanation: Minimum start value should be positive.
 *
 * Example 3:
 * Input: nums = [1,-2,-3]
 * Output: 5
 *
 * https://leetcode.com/problems/minimum-value-to-get-positive-step-by-step-sum
 */
class MinimumValueToGetPositiveStepByStepSum
{
    /**
     * @param int[] $nums
     * @return int
     */
    public function minStartValue(array $nums): int
    {
        $min = 0;
        $sum = 0;
        foreach ($nums as $num) {
            $sum += $num;
            if ($sum < $min) {
                $min = $sum;
            }
        }
        return 1 - $min;
    }
}