hdu 2491 Priest John's Busiest Day（动态规划之贪心）

http://acm.hdu.edu.cn/showproblem.php?pid=2491

#include<stdio.h>
#include<stdlib.h>
#define N 100008
struct cere
{
    int x,y;
    int mid,end;
}a[N];
int cmp(const void *a,const void *b)
{
    struct cere *c,*d;
    c=(struct cere *)a;
    d=(struct cere *)b;
    if(c->y!=d->y)
        return c->y-d->y;
    else
        return c->x-d->x;
}
int main()
{
    int n,i,x,y;
    while(scanf("%d",&n),n!=0)
    {
        for(i=0;i<n;i++)
        {
            scanf("%d%d",&x,&y);
            a[i].x=x;
            a[i].mid=(y-x)/2+1;
            a[i].y=x+a[i].mid;
            a[i].end=y;
        }
        qsort(a,n,sizeof(a[0]),cmp);
        int flag=0,time;
        time=0;
        for(i=0;i<n;i++)
        {
            if(time>(a[i].end-a[i].mid))
                break;
            if(time>=a[i].x)
                time+=a[i].mid;
            else
            time=a[i].y;
        }
        if(i>=n)
            printf("YES\n");
        else
            printf("NO\n");
    }
    return 0;
}