E. President and Roads (CF Round #Pi (Div. 2)) 优先队列的Dij+Tarjan找桥
思路：正反两遍求最短路，然后依据dist把那些最短路上的边又一次建图，注意是无向图，然后用Tarjan求割边。最后每条边推断输出。竟然卡SPFA，改成Dij就过了，以后就用Dij吧，恩。
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代码：
#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <cmath>
#include <string>
#include <map>
#include <stack>
#include <vector>
#include <set>
#include <queue>
#pragma comment (linker,"/STACK:102400000,102400000")
#define pi acos(-1.0)
#define eps 1e-6
#define lson rt<<1,l,mid
#define rson rt<<1|1,mid+1,r
#define FRE(i,a,b) for(i = a; i <= b; i++)
#define FREE(i,a,b) for(i = a; i >= b; i--)
#define FRL(i,a,b) for(i = a; i < b; i++)
#define FRLL(i,a,b) for(i = a; i > b; i--)
#define mem(t, v) memset ((t) , v, sizeof(t))
#define sf(n) scanf("%d", &n)
#define sff(a,b) scanf("%d %d", &a, &b)
#define sfff(a,b,c) scanf("%d %d %d", &a, &b, &c)
#define pf printf
#define DBG pf("Hi\n")
typedef __int64 ll;
using namespace std;
#define INF 0x3f3f3f3f
#define mod 1000000009
const int maxn = 1005;
const int MAXN = 100011;
const int MAXM = 250010;
const int N = 1005;
int n,m,s,t;
struct Edge
{
int u,v,next,id;
ll len;
}e1[MAXM],e2[MAXM];
int head1[MAXN],head2[MAXN];
typedef pair<ll,int>P;
ll dist1[MAXN],dist2[MAXN];
int num,tot,start,End;
bool cut[MAXN];
int Low[MAXN],DFN[MAXN],Stack[MAXN];
bool Instack[MAXN];
int Index,top;
void init()
{
num=0; tot=0;
mem(head1,-1);
memset(head2,-1,sizeof(head2));
}
void addedge(int u,int v,ll w,int id)
{
e1[num].u=u;
e1[num].v=v;
e1[num].len=w;
e1[num].id=id;
e1[num].next=head1[u];
head1[u]=num++;
}
void addedge2(int u,int v,ll w,int id)
{
e2[tot].u=u;
e2[tot].v=v;
e2[tot].len=w;
e2[tot].id=id;
e2[tot].next=head2[u];
head2[u]=tot++;
}
void Dijkstra(int s,int t,int head[],ll dist[],Edge edge[])
{
priority_queue<P,vector<P>,greater<P> >Q;
dist[s]=0;
Q.push(make_pair(0,s));
while (!Q.empty())
{
P p=Q.top(); Q.pop();
int u=p.second;
if (dist[u]<p.first) continue;
for (int i=head[u];~i;i=edge[i].next)
{
int v=edge[i].v;
if (dist[v]>dist[u]+edge[i].len)
{
dist[v]=dist[u]+edge[i].len;
Q.push(make_pair(dist[v],v));
}
}
}
}
void Tarjan(int u,int pre)
{
int v;
Low[u]=DFN[u]=++Index;
Stack[top++]=u;
Instack[u]=true;
int pre_cnt=0;
for (int i=head2[u];~i;i=e2[i].next)
{
v=e2[i].v;
if (v==pre&&pre_cnt==0) { pre_cnt++;continue; }
if (!DFN[v])
{
Tarjan(v,u);
if (Low[u]>Low[v]) Low[u]=Low[v];
if (Low[v]>DFN[u])
cut[e2[i].id]=true;
}
else if (Low[u]>DFN[v])
Low[u]=DFN[v];
}
Instack[u]=false;
top--;
}
void solve()
{
memset(DFN,0,sizeof(DFN));
memset(Instack,false,sizeof(Instack));
Index=top=0;
for (int i=1;i<=n;i++)
if (!DFN[i])
Tarjan(i,i);
}
int main()
{
#ifndef ONLINE_JUDGE
freopen("C:/Users/lyf/Desktop/IN.txt","r",stdin);
#endif
int i,j,u,v;
ll w;
while (~scanf("%d%d%d%d",&n,&m,&s,&t))
{
init();
for (i=0;i<m;i++)
{
scanf("%d%d%I64d",&u,&v,&w);
addedge(u,v,w,i);
addedge2(v,u,w,i);
}
mem(dist1,INF);
mem(dist2,INF);
Dijkstra(s,t,head1,dist1,e1);
Dijkstra(t,s,head2,dist2,e2);
tot=0;
memset(head2,-1,sizeof(head2));
for (i=0;i<m;i++)
{
cut[i]=false;
u=e1[i].u;
v=e1[i].v;
if (dist1[u]+dist2[v]+e1[i].len==dist1[t])
{
addedge2(u,v,e1[i].len,i);
addedge2(v,u,e1[i].len,i);
}
}
solve();
for (i=0;i<m;i++)
{
u=e1[i].u;
v=e1[i].v;
if (cut[i]) printf("YES\n");
else if (dist1[u]+dist2[v]+e1[i].len==dist1[t])
{
if (e1[i].len>1)
printf("CAN 1\n");
else
printf("NO\n");
}
else
{
ll dd=dist1[t]-dist1[u]-dist2[v]-1;
if (dd<=0)
printf("NO\n");
else
printf("CAN %I64d\n",e1[i].len-dd);
}
}
}
return 0;
}
