Luogu P1608 路径统计 最短路计数

颓了、、、重边导致我乖乖用邻接矩阵。。。。

如果d[v]>d[u]+w[i]，那么c[v]直接赋值为c[u]，相当于这个最短路是由u转移过来的、

#include<cstdio>
#include<iostream>
#include<cstring>
#include<queue>
#define R register int
using namespace std;
const int N=2010,M=4000010;
inline int g() {
    R ret=0,fix=1; register char ch; while(!isdigit(ch=getchar())) fix=ch==‘-‘?-1:fix;
    do ret=ret*10+(ch^48); while(isdigit(ch=getchar())); return ret*fix;
}
int n,m,cnt;
int w[N][N],fir[N],d[N],c[N];
bool vis[N];
priority_queue<pair<int,int> > q;
inline void dijk() {
    memset(d,0x3f,sizeof(int)*(n+2)); c[1]=1,d[1]=0,q.push(make_pair(0,1));
    while(q.size()) {
        R u=q.top().second; q.pop(); if(vis[u]) continue; vis[u]=true;
        for(R i=1;i<=n;++i) {
            if(d[i]>d[u]+w[u][i]) d[i]=d[u]+w[u][i],q.push(make_pair(-d[i],i)),c[i]=c[u];
            else if(d[i]==d[u]+w[u][i]) c[i]+=c[u];
        }
    }
}
signed main() { freopen("in.in","r",stdin);
    n=g(),m=g(); memset(w,0x3f,sizeof(w)); for(R i=1,u,v,ww;i<=m;++i) u=g(),v=g(),ww=g(),w[u][v]=min(w[u][v],ww);
    dijk(); if(d[n]==0x3f3f3f3f) printf("No answer\n"); else printf("%d %d\n",d[n],c[n]);
}

原文地址：https://www.cnblogs.com/Jackpei/p/10765789.html