poj 2037 今年暑假不AC

简单贪心，选择不相交区间：

#include<stdio.h>
#include<stdlib.h>

int n, s[25], e[25], r[25];

int cmp(const void *_p, const void *_q)
{
    int *p = (int *)_p;
    int *q = (int *)_q;
    return e[*p]-e[*q];
}

int main()
{
    while(scanf("%d",&n))
    {
        if(n == 0) break;
        for(int i = 0; i < n; i ++)
        {
            scanf("%d%d",&s[i],&e[i]);
            r[i] = i;        
        }
        qsort(r,n,sizeof(r[0]),cmp);
        int ans = -1, count = 0;
        for(int i = 0; i < n; i ++)
            if(s[r[i]] >= ans){ans = e[r[i]]; count ++;}
        printf("%d\n",count);
    }    
    return 0;
}