URAL1303——贪心——Minimal Coverage

#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;
struct edge{
    int b,e;
}t[100010];
bool vis[100010];
bool cmp(edge i,edge j){
    if(i.b == j.b)
        return i.e < j.e;
    return i.b < j.b;
}
int main()
{
    int M;
    int x,y;
    while(~scanf("%d",&M)){
        int count = 1;
        memset(vis,false,sizeof(vis));
        while(~scanf("%d%d",&x,&y)){
            if(x == 0 && y == 0) break;
            if(y <= 0 || x >= M || x == y)
                continue;
            t[count].b = x;
            t[count++].e = y;
        }
        sort(t+1, t+count,cmp);
        int end = 0,pos = 1;
        int flag = 1,res = 0;;
        while(end < M){
            int end1 = 0,npos = 1;
            while(pos < count && t[pos].b <= end){
                if(t[pos].e > end1){
                    end1 = t[pos].e;
                    npos = pos;
                }
                pos++;
            }
            if(end1 == 0) {flag = 0 ;break;}
            end = end1;
            vis[npos] = 1;
            res++;
        }
        if(flag == 0) printf("No solution\n");
        else {
            printf("%d\n",res);
            for(int i = 1; i < count ;i++){
                if(vis[i])
                    printf("%d %d\n",t[i].b,t[i].e);
            }
        }
    }
        return 0;
    }