leetcode.209. Minimum Size Subarray Sum

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.

class Solution {
public:
int minSubArrayLen(int s, vector<int>& nums) {
if(nums.size()==0||s<0)
return 0;

int start = 0;
int end = 0;

int sum = 0;
int len = INT_MAX;

while(start<nums.size() && end<nums.size()) {
while(sum<s && end<nums.size()) {
sum += nums[end++];
}
while(sum>=s && start<=end) {
len = min(len,end-start);
sum -= nums[start++];
}
}

return len == INT_MAX ? 0 : len;

}
};