HDU 1142

University of Waterloo Local Contest 2005.09.24

Dijkstra

#include<iostream>
#include<cstdio>
#include<cstring>
#include<cstdlib>
#include<algorithm>
#include<vector>
#include<queue>
using namespace std;
int n,m;
const int maxn=2010;
const int inf=0x3ffffff;
int cost[maxn][maxn];
int num[maxn];
bool uesd[maxn];
int d[maxn];
void dijkstra(int s)
{
     for(int i=0;i<=n;i++)
     {
         d[i]=inf;
         uesd[i]=0;
     }
     d[s]=0;
     while(1){
        int v=-1;
        for(int i=1;i<=n;i++)
        {
            if(!uesd[i]&&(v==-1||d[i]<d[v])) {v=i;}
        }
        uesd[v]=1;
        if(v==-1) break;
        for(int i=1;i<=n;i++)
        {
            if(d[i]>d[v]+cost[i][v]) {d[i]=d[v]+cost[i][v];}
        }
     }
}
int bfs(int s)
{
    if(num[s]) return num[s];
    if(s==2) return 1;
    int sum=0;
    for(int i=1;i<=n;i++)
    {
        if(cost[s][i]<inf&&d[s]>d[i]){
            if(num[i]) sum=sum+num[i];
            else sum=sum+bfs(i);
        }
    }
    sum=sum+num[s];
    num[s]=sum;
    return num[s];
}
int main()
{
    int a,b,c;
    while(1){
            scanf("%d",&n);
        if(!n) break;
        for(int i=0;i<=n;i++)
           for(int j=0;j<=n;j++)
            cost[i][j]=inf;
       for(int i=0;i<=n;i++) cost[i][i]=0;
        scanf("%d",&m);
        for(int i=1;i<=m;i++)
        {
            scanf("%d%d%d",&a,&b,&c);
            cost[a][b]=cost[b][a]=c;
        }
        dijkstra(2);
        memset(num,0,sizeof(num));
         printf("%d\n",bfs(1));
    }

Heap+Dijkstra

#include<iostream>
#include<cstdio>
#include<cstring>
#include<cstdlib>
#include<algorithm>
#include<vector>
#include<queue>
using namespace std;
int n,m;
const int maxn=2007;
const int inf=0x3fffffff;
bool flag[maxn][maxn];
int num[maxn];
struct HeapNode
{
    int d,u;
    HeapNode(int dd,int uu):d(dd),u(uu){}
    bool operator < (const HeapNode& rhs) const{
       return d>rhs.d;
       }
};
struct Edge
{
    int from,to,dist;
    Edge(int u,int v,int d):from(u),to(v),dist(d){}
};
vector<Edge> edges;
vector<int> G[maxn];
bool done[maxn];
int d[maxn],p[maxn];
void init(){
  for(int i=0;i<=n;i++) G[i].clear();
  edges.clear();
}
void AddEdge(int from,int to,int dist)
{
    int mm;
    edges.push_back(Edge(from,to,dist));
    mm=edges.size();
    G[from].push_back(mm-1);
}
void dijkstra(int s)
{
     priority_queue<HeapNode> Q;
     for(int i=0;i<=n;i++) d[i]=inf;
     d[s]=0;
     memset(done,0,sizeof(done));
     Q.push(HeapNode(0,s));
     while(!Q.empty()){
        HeapNode x=Q.top();Q.pop();
        int u=x.u;
        if(done[u]) continue;
        done[u]=true;
        for(int i=0;i<G[u].size();i++){
            Edge& e=edges[G[u][i]];
            if(d[e.to]>d[u]+e.dist){
                d[e.to]=d[u]+e.dist;
                p[e.to]=G[u][i];
                Q.push(HeapNode(d[e.to],e.to));
            }
        }
     }
}
int bfs(int s)
{
    if(num[s]) return num[s];
    if(s==2) return 1;
    int sum=0;
    for(int i=1;i<=n;i++)
    {
        if(flag[s][i]&&d[s]>d[i]){
            if(num[i]) sum=sum+num[i];
            else sum=sum+bfs(i);
        }
    }
    sum=sum+num[s];
    num[s]=sum;
    return num[s];
}
int main()
{
    int a,b,c;
    while(1){
        memset(flag,0,sizeof(flag));
        scanf("%d",&n);
        init();
        if(!n) break;
        scanf("%d",&m);
        for(int i=1;i<=m;i++)
        {
            scanf("%d%d%d",&a,&b,&c);
            AddEdge(a,b,c);
            AddEdge(b,a,c);
           flag[a][b]=flag[b][a]=1;
        }
        dijkstra(2);
        memset(num,0,sizeof(num));
        int ans=0;
         int  sum=d[1];
         for(int i=3;i<=n;i++)
         {
             if(d[i]<sum) ans++;
         }
         printf("%d\n",bfs(1));
    }
}

HDU 1142

原文：http://blog.csdn.net/yuanchang_best/article/details/43156625