hdu 2544 最短路

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思路：  模板题，求解最短路的四种算法都可以。注意求解最短路时候要处理成无向图

代码：

/*Dijkstra*/
#include<iostream>
#include<algorithm>
#include<cstdio>
#include<cstring>
using namespace std;
#define MAXN 110
#define INF 0xFFFFFFF

int n , m;
int  value[MAXN][MAXN];
int  dis[MAXN];

void Dijkstra(){
     int pos;
     int vis[MAXN];
     memset(vis , 0 , sizeof(vis));
     dis[1] = 0;
     for(int i = 2 ; i <= n ; i++)
        dis[i] = INF;
     for(int i = 1 ; i <= n ; i++){
         pos = -1;
         for(int j = 1 ; j <= n ; j++){
            if(!vis[j] && (pos == -1 || dis[j] < dis[pos]))
               pos = j;
         }
         vis[pos] = 1;
         for(int j = 1 ; j <= n ; j++){
            if(!vis[j] && dis[j] > dis[pos] + value[pos][j])
               dis[j] = dis[pos] + value[pos][j];
         }
     }
     printf("%d\n" , dis[n]);
}

int main(){
    //freopen("input.txt" , "r" , stdin);
    int star , end , v;
    while(scanf("%d%d" , &n , &m) , n+m){
       for(int i = 1 ; i <= n ; i++){
          for(int j = 1 ; j <= n ; j++)
             value[i][j] = INF;
       }
       for(int i = 0 ; i < m ; i++){
          scanf("%d%d%d" , &star , &end , &v);
          if(value[star][end] != INF)
            value[star][end] = value[end][star] = v;
          else{
            if(value[star][end] > v)
               value[star][end] = value[end][star] = v;
          }
       }
       Dijkstra();
    }
    return 0;
}

/*floyd*/
/*floyd*/
#include<iostream>
#include<algorithm>
#include<cstdio>
#include<cstring>
using namespace std;
#define MAXN 110
#define INF 0xFFFFFFF

int n , m;
long long dis[MAXN][MAXN];

void init(){
    for(int i = 1 ; i <= n ; i++){
       for(int j = 1 ; j <= n ; j++){
          if(i == j)
            dis[i][j] = 0;
          else
            dis[i][j] = INF;
       }
    }
}

long long min(int a , int b){
     return a < b ? a : b;
}

void floyd(){
     for(int k = 1 ; k <= n ; k++){
       for(int i = 1 ; i <= n ; i++){
          for(int j = 1 ; j <= n ; j++)
             dis[i][j] = min(dis[i][k]+ dis[k][j] , dis[i][j]);
       }
     }
     printf("%lld\n" , dis[1][n]);
}

int main(){
    //freopen("input.txt" , "r" , stdin);
    int a , b , value;
    while(scanf("%d%d" , &n , &m) , n+m){
         init();
         for(int i = 0 ; i < m ; i++){
            scanf("%d%d%d" , &a , &b , &value);
            dis[a][b] = dis[b][a] = value;
         }
         floyd();
    }
    return 0;
}

/*Bellman_Ford*/
#include<iostream>
#include<algorithm>
#include<cstdio>
#include<cstring>
using namespace std;
#define MAXN 20010
#define INF 0xFFFFFFF

int n , m;
long long dis[MAXN];
struct Edge{
   int x;
   int y;
   int value;
}e[MAXN];

void Bellman_Ford(){
     dis[1] = 0;
     for(int i = 2 ; i <= n ; i++)
        dis[i] = INF;
     for(int i = 1 ; i < n ; i++){
       for(int j = 0 ; j < 2*m ; j++){
          if(dis[e[j].y] > dis[e[j].x] + e[j].value)
            dis[e[j].y] = dis[e[j].x] + e[j].value;
       }
     }
     printf("%lld\n" , dis[n]);
}

int main(){
    //freopen("input.txt" , "r" , stdin);
    while(scanf("%d%d", &n , &m) , n+m){
        for(int i = 0 ; i < m ; i++){
           scanf("%d%d%d" , &e[i].x , &e[i].y , &e[i].value);
           e[i+m].x = e[i].y;
           e[i+m].y = e[i].x;
           e[i+m].value= e[i].value;
        }
        Bellman_Ford();
    }
    return 0;
}

/*SPFA*/
#include<iostream>
#include<algorithm>
#include<cstdio>
#include<cstring>
#include<queue>
using namespace std;
#define MAXN 20010
#define INF 0xFFFFFFF

int n , m;
int first[MAXN] , next[MAXN];
int star[MAXN] , end[MAXN] , value[MAXN];
int dis[MAXN];
int vis[MAXN];
queue<int>q;

void init(){
    memset(first , -1 , sizeof(first));
    memset(next , -1 , sizeof(next));
    memset(vis , 0 , sizeof(vis));
}

void SPFA(){
    dis[1] = 0;
    for(int i = 2 ; i <= n ; i++)
       dis[i] = INF;
    vis[1] = 1;
    while(!q.empty())
       q.pop();
    q.push(1);
    while(!q.empty()){
        int tmp = q.front();
        q.pop();
        vis[tmp] = 0;
        for(int i = first[tmp] ; i != -1 ; i = next[i]){
           if(dis[end[i]] > dis[tmp] + value[i]){
              dis[end[i]] = dis[tmp ] + value[i];
              if(!vis[end[i]]){
                 vis[end[i]] = 1;
                 q.push(end[i]);
              }
           }
        }
    }
    printf("%d\n" , dis[n]);
}

int main(){
    //freopen("input.txt" , "r" , stdin);
    while(scanf("%d%d" , &n , &m) , n+m){
        init();
        /*处理成无向图*/
        for(int i = 0 ; i < m ;i++){
           scanf("%d%d%d" , &star[i] , &end[i] , &value[i]);
           star[i+m] = end[i];
           end[i+m] = star[i];
           value[i+m] = value[i];

           next[i] = first[star[i]];
           first[star[i]] = i;
           next[i+m] = first[star[i+m]];
           first[star[i+m]] = i+m;
        }
        SPFA();
    }
    return 0;
}