(贪心5.2.9)UVA 10020 Minimal coverage(利用数据有序化来进行贪心选择)

/*
 * UVA_10020.cpp
 *
 *  Created on: 2013年10月11日
 *      Author: Administrator
 */

#include <iostream>
#include <cstdio>
#include <algorithm>

using namespace std;

const int maxn = 100005;
struct line {
	int l;
	int r;

	bool operator<(const line& n) const{
		if( l != n.l){
			return l < n.l;
		}else{
			return r > n.r;
		}
	}

}lines[maxn];


int main() {

	int t;
	scanf("%d", &t);
	while (t--) {
		line s[maxn];

		int m;
		scanf("%d", &m);
		int l, r;

		int now=0, len=0, num = 0, ans = 0;
		while (scanf("%d%d", &l, &r) != EOF, l || r) {
			lines[num].l = l;
			lines[num++].r = r;
		}


		sort(lines,lines+num);
		int i;
		int k;


		bool flag =false;
		for (i = 0; i < num; ++i) {

			if(lines[i].l > now){
				flag = false;
				break;
			}

			if(lines[i].r > now){
				if(lines[i].r > len){
					len = lines[i].r;
					k = i;
				}

				if(lines[i+1].l > now || i + 1 == num){

					now = len;
					len = 0;
					s[ans++] = lines[k];
				}
			}

			if(now >= m){
				flag = true;
				break;
			}
		}

		if(!flag){
			printf("0\n");
		}else{
			printf("%d\n",ans);
			for(i = 0 ; i < ans ; ++i){
				printf("%d %d\n",s[i].l,s[i].r);
			}


		}

		if(t){
			printf("\n");
		}

	}

	return 0;
}