leetcode_209题——Minimum Size Subarray Sum（两个指针）

Minimum Size Subarray Sum

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Question Solution

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.

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Credits:
Special thanks to @Freezen for adding this problem and creating all test cases.

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这道题采用的是两个指针（滑动窗口的方法），先从0开始找到一个窗口，然后通过这两个指针来移动窗口和改变窗口的大小，再保存一个最小值。一直到最后。

#include<iostream>
#include<vector>
using namespace std;

int minSubArrayLen(int s, vector<int>& nums) {
	int n=nums.size();
	int start=0;
	int end=0;
	int min;
	int sum=0;
	while(end<n)
	{
		sum+=nums[end];
		if(sum>=s)
		{
			min=end+1;
			break;
		}
		end++;
	}
	if(end>=n)
		return 0;
	while(end<n)
	{
		if(sum>=s)
		{
			while(start<=end)
			{
				sum-=nums[start];
				start++;
				if(sum>=s)
				{
					int a=end-start+1;
					if(a<min)
						min=a;
				}
				else
					break;
			}
			if(end<n&&start<end)
			{
				end++;
				sum+=nums[end];
			}
			else
				break;
		}
		else
		{
			end++;
			if(end>n)
				break;
			else
				sum+=nums[end];
		}
	}
	return min;
}

int main()
{
	int a[6]={2,3,1,2,4,3};
	vector<int> vec(a,a+6);
	cout<<minSubArrayLen(7,vec)<<endl;
}