A. Counting Kangaroos is Fun（贪心）

#include<stdio.h>

#include<algorithm>

using namespace std;

int a[1000100];

int main()

{

    int i,n,high;

    while(scanf("%d",&n)!=EOF)

    {

        for(i=0;i<n;i++)

            scanf("%d",&a[i]);

        sort(a,a+n);

        int ans=n;

        high=n-1;

        for(i=n/2-1;i>=0;i--)//i=n/2-1容易出错

        {

            if(a[i]*2<=a[high])

            {

                ans--;

                high--;

            }

        }

        printf("%d\n",ans);

    }

    return 0;

}

从中间开始贪心Each kangaroo can hold at most one kangaroo