這道題有毒啊。。輸出的不是“NO”是“N0”，不是“YES”而是“YE5”。被坑了一晚上。 另外，spfa-dfs竟然被卡死了，只能過9個點。換成三行就寫完的Bellmam-Ford就AC了

SPFA-DFS程式碼：

#include<bits/stdc++.h>
#define rep(i,l,r) for(int i=(l);i<=(r);i++)
#define per(i,r,l) for(int i=(r);i>=(l);i--)
#define random(l,r) ((l)+rand()%((r)-(l)+1))
using namespace std;
typedef unsigned long long ull;
typedef long long ll;
typedef pair<int,int> pii;
const int inf=1e9+10,N=210000,M=2e5+100000;
const double eps=1e-6;
int n,m,dis[N],t,minedge;
int head[N],nxt[M],to[M],w[M],len;
bool ex,vis[N];
int sign,v; char c;
inline int read(){
	sign=v=0;
	while(!isdigit(c=getchar())) if(c=='-') break;
	if(c=='-') sign=-1; else v=c-'0';
	while(isdigit(c=getchar())) v=v*10+c-'0';
	if(sign==0) return v; else return -v;
}
inline void addedge(int a,int b,int ww){ nxt[++len]=head[a]; head[a]=len; to[len]=b; w[len]=ww; }
void spfa(int v){
	if(ex) return;
	vis[v]=true;
	for(int i=head[v];i!=-1;i=nxt[i]){
		int u=to[i];
		if(dis[u]<minedge-70100){
			ex=true;
			return;
		}
		if(dis[v]+w[i]<dis[u]){
			dis[u]=dis[v]+w[i];
			if(!vis[u]) spfa(u); else ex=true;
			if(ex) return;
		}
	}
	vis[v]=false;
}
bool negative_loop_detect(){
	ex=false;
	memset(dis,0,sizeof(dis));
	memset(vis,false,sizeof(vis));
	rep(i,1,n){
		spfa(i);
		if(ex) return true;
	}
	return false;
}
int x,y,z;
int main(){
	int t=read(); minedge=inf;
	while(t--){
		memset(head,-1,sizeof(head)); len=0;
		n=read(); m=read();
		rep(i,1,m){
			x=read(); y=read(); z=read();
			addedge(x,y,z); minedge=min(minedge,z);
			if(z>=0) addedge(y,x,z);
		}
		if(negative_loop_detect()) puts("YE5");
			else puts("N0");
	}
	return 0;
}
 

Bellman-Ford程式碼：

#include<bits/stdc++.h>
#define rep(i,l,r) for(int i=(l);i<=(r);i++)
#define per(i,r,l) for(int i=(r);i>=(l);i--)
#define random(l,r) ((l)+rand()%((r)-(l)+1))
using namespace std;
typedef unsigned long long ull;
typedef long long ll;
typedef pair<int,int> pii;
const int inf=1e9+10,N=210000,M=2e5+100000;
const double eps=1e-6;
int n,m,dis[N],t,minedge;
int head[N],nxt[M],to[M],w[M],len;
bool ex,vis[N];
int sign,v; char c;
inline int read(){
	sign=v=0;
	while(!isdigit(c=getchar())) if(c=='-') break;
	if(c=='-') sign=-1; else v=c-'0';
	while(isdigit(c=getchar())) v=v*10+c-'0';
	if(sign==0) return v; else return -v;
}
inline void addedge(int a,int b,int ww){ nxt[++len]=head[a]; head[a]=len; to[len]=b; w[len]=ww; }
bool bellmanford(){
	memset(dis,0x3f,sizeof(dis)); dis[1]=0;
	rep(k,1,n-1) rep(v,1,n) for(int i=head[v];i!=-1;i=nxt[i]) dis[to[i]]=min(dis[to[i]],dis[v]+w[i]);
	rep(v,1,n) for(int i=head[v];i!=-1;i=nxt[i]) if(dis[to[i]]>dis[v]+w[i]) return true;
	return false;
}
int x,y,z;
int main(){
	t=read(); minedge=inf;
	while(t--){
		memset(head,-1,sizeof(head)); len=0;
		n=read(); m=read();
		rep(i,1,m){
			x=read(); y=read(); z=read();
			addedge(x,y,z); //minedge=min(minedge,z);
			if(z>=0) addedge(y,x,z);
		}
		if(bellmanford()) puts("YE5");
			else puts("N0");
	}
	return 0;
}