leetcode/work/Easy/Array/1413.minimum-value-to-get-positive-step-by-step-sum.js

/*
 * 1413. Minimum Value to Get Positive Step by Step Sum
 * Difficulty: Easy
 * https://leetcode.com/problems/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
 * 
 *  
 * 
 * Constraints:
 * 
 * 	• 1 <= nums.length <= 100
 * 
 * 	• -100 <= nums[i] <= 100
*/

/**
 * @param {number[]} nums
 * @return {number}
 */
var minStartValue = function(nums) {
  let prefix = [nums[0]];
  // Make prefix sum start at 1 after initializing seed value
  for (let i = 1; i < nums.length; i++){
    prefix.push(prefix[i - 1] + nums[i]);
  }

  let min = Math.min(...prefix);
  return Math.max(1, 1 - min);
};