UVA 10020 Minimal coverage

题意：已知M，以及多个区间，求能覆盖[0,M]的最少的区间。

#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;
struct node
{
    int l,r;
}q[100005],ans[100005];
int cmp(node a,node b)
{
    return a.r>b.r;
}
int main()
{
    int t,M,num1,num2,s;
    scanf("%d",&t);
    while(t--)
    {
        num1=0;
        num2=0;
        s=0;
        scanf("%d",&M);
        memset(q,0,sizeof(q));
        memset(ans,0,sizeof(ans));
        while(~scanf("%d%d",&q[num1].l,&q[num1].r))
        {
            if(q[num1].l+q[num1].r==0)
                break;
            num1++;
        }

        sort(q,q+num1,cmp);
        while(s<M)
        {
            int i;
            for(i=0;i<num1;++i)
            {
                if(q[i].l<=s&&q[i].r>s)
                {
                    s=q[i].r;
                    ans[num2++]=q[i];
                    break;
                }
            }
            if(i==num1)
            break;
    }
    if(s<M)
        printf("0
");

    else
    {
        printf("%d
",num2);
        for(int i=0;i<num2;++i)
        printf("%d %d
",ans[i].l,ans[i].r);
    }
    if(t)
      printf("
");
    }
    return 0;
}