MinimumSizeSubarraySum.java

package com.fishercoder.solutions;

/**
 * Given an array of n positive integers and a positive integer s, find the minimal length of a contiguous subarray of which the sum ≥ s. If there isn't one, return 0 instead.

 For example, given the array [2,3,1,2,4,3] and s = 7,
 the subarray [4,3] has the minimal length under the problem constraint.

 click to show more practice.

 More practice:
 If you have figured out the O(n) solution, try coding another solution of which the time complexity is O(n log n).
 */
public class MinimumSizeSubarraySum {

    public int minSubArrayLen(int s, int[] nums) {
        if(nums == null || nums.length == 0) return 0;
        int i = 0, j = 0, min = Integer.MAX_VALUE, sum = 0;
        while(j < nums.length){
            sum += nums[j++];

            while(sum >= s){
                min = Math.min(min, j-i);
                sum -= nums[i++];
            }
        }
        return min == Integer.MAX_VALUE ? 0 : min;
    }

}