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;

}