LeetCode 209. Minimum Size Subarray Sum (javascript)

Given an array of positive integers nums and a positive integer target, return the minimal length of a contiguous subarray [numsl, numsl+1, ..., numsr-1, numsr] of which the sum is greater than or equal to target. If there is no such subarray, return 0 instead.

Example 1:

Input: target = 7, nums = [2,3,1,2,4,3]
Output: 2
Explanation: The subarray [4,3] has the minimal length under the problem constraint.

Example 2:

Input: target = 4, nums = [1,4,4]
Output: 1

Example 3:

Input: target = 11, nums = [1,1,1,1,1,1,1,1]
Output: 0

Constraints:

• 1 <= target <= 109
• 1 <= nums.length <= 105
• 1 <= nums[i] <= 105

Idea:

Two pointers + tracking min size

Solution:

/**
 * @param {number} target
 * @param {number[]} nums
 * @return {number}
 */
var minSubArrayLen = function(target, nums) {
    let l = 0;
    let r = 0;
    let ans = Infinity;
    const n = nums.length;
    let total = 0;
    while (l < n) {
        while(r < n && total < target) {
            total += nums[r];
            r++;
        }
        if (total < target) break;
        ans = Math.min(ans, r - l);
        total -= nums[l];
        l++;
    }
    return ans === Infinity ? 0 : ans;
};