LeetCode-Minimum Size Subarray Sum-解题报告

原题链接 https://leetcode.com/problems/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. 

设置有一个start和sum,然后遍历数组，当 sum>= s 的时候，start往后走，直到 sum 不小于 s，更新start。

class Solution {
public:
int minSubArrayLen(int s, vector<int>& nums) {
if (nums.empty())return 0;
long long sum = 0, cnt = 1, start = 0, ans = nums.size() + 1;
for (int i = 0; i < nums.size(); ++i)
{
sum += nums[i];
cnt++;
if (sum >= s)
{
while (sum - nums[start] >= s)
sum -= nums[start], start++, cnt--;
if (ans > cnt)ans = cnt;
}

}
return ans > nums.size()? 0 : ans - 1;
}
};