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
思路：尺取即可。。好久没写，竟然调了半天。。。
1/* ***********************************************
2Author :111qqz
3Created Time :2017年04月13日 星期四 20时48分00秒
4File Name :209.cpp
5************************************************ */
6class Solution {
7
8public:
9
10 int ruler(vector<int>nums,int tar,int n)
11 {
12 int head = 0;
13 int tail = 0;
14 int sum = 0 ;
15 int res = 0x3f3f3f3f;
16 while (tail<n&&head<=tail)
17 {
18 sum = sum + nums[tail];
19 if (sum>=tar)
20 {
21 res = min(res,tail-head+1);
22 while (sum>=tar&&head<tail)
23 {
24 sum-=nums[head];
25 head++;
26 }
27 if (sum>=tar)
28 {
29 res = min(res,tail-head+1);
30 }
31 else
32 {
33 head--;
34 sum+=nums[head];
35 res = min(res,tail-head+1);
36 }
37 }
38
39
40
41 tail++;
42 }
43 return res==0x3f3f3f3f?0:res;
44 }
45
46
47 int minSubArrayLen(int s, vector<int>& nums) {
48 int n = nums.size();
49 int res = ruler(nums,s,n);
50 return res;
51
52
53 }
54
55};