HDU 2491 Priest John's Busiest Day

贪心。。

#include<iostream>
#include<string.h>
#include<math.h>
#include <stdio.h>
#include <algorithm>

using namespace std;

struct node
{
    int s,t;
    int m;
};

node a[100010];

int cmp(node a,node b)
{
    return a.m<b.m;
}

int main()
{
    int n;
    int i,j;
    int now;
    while(scanf("%d",&n)!=EOF)
    {
        if(n==0)
            break;
        for(i=0;i<n;i++)
        {
            scanf("%d%d",&a[i].s,&a[i].t);
            if((a[i].t-a[i].s)%2==0)
                a[i].m=a[i].s+(a[i].t-a[i].s)/2-1;
            else
                a[i].m=a[i].s+(a[i].t-a[i].s)/2;
        }
        sort(a,a+n,cmp);
        now=0;
        int flag=0;
        int cnt=0;
        for(i=0;i<n;i++)   
        { 
            if(now>a[i].m)
            {
                flag=1;
                break;
            }
            else if(now<=a[i].s)
                now=a[i].s+(a[i].t-a[i].s)/2+1;
            else if(now>a[i].s)
                now=now+(a[i].t-a[i].s)/2+1;
            cnt++;
        }

        if(flag)
            printf("NO
");
        else 
        {
            if(cnt==n)
                printf("YES
");
            else 
                printf("NO
");
        }
    }
    return 0;
}