51Nod 1091 线段的重叠 贪心

注意减枝

#include<iostream>  
#include<cstdio>  
#include<cstring>  
#include<cmath>  
#include<algorithm>  
#include<queue>  
#include<stack>  
using namespace std;
typedef struct node{
	int x,y;
}node; 
bool cmp(node n1,node n2){
	return n1.x<n2.x;
}
int main(){
	node no[50000+10];
	int n;
	scanf("%d",&n);
	for(int i=0;i<n;i++){
		scanf("%d%d",&no[i].x,&no[i].y);
	}
	sort(no,no+n,cmp);
	int maxn=0;
	for(int i=0;i<n;i++){
		for(int j=i+1;j<n;j++){
			if(no[j].x>no[i].y) break;
			if(no[j].y<=no[i].y){
				if(no[j].y-no[j].x>maxn) maxn=no[j].y-no[j].x;
			}
			else{
				if(no[i].y-no[j].x>maxn) maxn=no[i].y-no[j].x;
				break;
			}
		}
	}
	cout<<maxn;
    return 0;  
}