yzoj P2350 逃离洞穴 题解

题意

跑两边spfa的水题,注意判断有人才取最大值

代码

#include<bits/stdc++.h>
using namespace std;
inline int read(){
    int x=0,f=1;
    char ch=getchar();
    while(ch<'0'||ch>'9'){
        if(ch=='-')
            f=-1;
        ch=getchar();
    }
    while(ch>='0'&&ch<='9'){
        x=(x<<1)+(x<<3)+(ch^48);
        ch=getchar();
    }
    return x*f;
}
const int N=510,M=100010;
int head[N],ver[M],edge[M],Next[M],d1[N],d2[N],d[N],op[N];
int n,m,k,T,tot,maxn;
queue<int> q;
bool v[N];
long long ans;
void add(int x,int y,int z){
	ver[++tot]=y;edge[tot]=z;Next[tot]=head[x],head[x]=tot;
}
void spfa(){
	memset(d1,0x3f,sizeof(d1));
	d1[1]=0,v[1]=1;
	q.push(1);
	while(q.size()){
		int x=q.front();q.pop();
		v[x]=0;
		for(int i=head[x];i;i=Next[i]){
			int y=ver[i],z=edge[i];
			if(d1[y]>d1[x]+z){
				d1[y]=d1[x]+z;
				if(!v[y]) q.push(y),v[y]=1;
			}
		}
	}
	memset(d2,0x3f,sizeof(d2));
	memset(v,0,sizeof(v));
	d2[n]=0,v[n]=1;
	q.push(n);
	while(q.size()){
		int x=q.front();q.pop();
		v[x]=0;
		for(int i=head[x];i;i=Next[i]){
			int y=ver[i],z=edge[i];
			if(d2[y]>d2[x]+z){
				d2[y]=d2[x]+z;
				if(!v[y]) q.push(y),v[y]=1;
			}
		}
	}
	for(int i=1;i<=n;++i){
		d[i]=min(d1[i],d2[i]);
	}
}
int main(){
	freopen("escape.in","r",stdin);
	freopen("escape.out","w",stdout);
	n=read();m=read();T=read();
	for(int i=1;i<=m;++i){
		int x,y,z;
		x=read();y=read();z=read();
		add(x,y,z);
		add(y,x,z);
	}
	spfa();
	k=read();
	int tmp;
	for(int i=1;i<=k;++i){
		tmp=read();
		op[tmp]++;
	}
	for(int i=1;i<=n;++i){
		if(d[i]<=T)  ans+=op[i];
		if(op[i]) maxn=max(maxn,min(d1[i],d2[i]));
	}
	printf("%lld\n%d",ans,maxn);
	return 0;
}
/*
4 4 3
1 2 5
2 4 3
1 3 4
3 4 6
4
1 2 3 4
*/
posted @ 2019-08-27 09:47  End_donkey  阅读(139)  评论(0编辑  收藏  举报