209. Minimum Size Subarray Sum

题目：

Given an array of n positive integers and a positive integer s, find the minimal length of a 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).

解题思路：
利用滑动窗口的思想

class Solution {
public:
int minSubArrayLen(int s, vector<int>& nums) {
int i=0,j=0;
int sum = 0,min=INT_MAX;

while(j<nums.size())
{
while(j<nums.size() and sum<s)sum += nums[j++];
if(sum>=s)
{
while(sum>=s and i<j) sum -= nums[i++];
min = min<(j-i+1) ? min:j-i+1;
}
}
return min==INT_MAX ? 0:min;
}
};