poj2263

最短路

map如果要使用char*作为key，不能简单的直接使用，可以用string作为map的key，使用的时候将char*转换为string。转换的方法是使用string的assign函数。string.assign(char*);

#include <iostream>

#include <cstdlib>

#include <cstdio>

#include <cstring>

#include <algorithm>

#include <map>

using namespace std;



#define maxn 205

#define maxm 20005

#define maxl 50



struct Edge

{

    int v, w, next;

}edge[maxm * 2];



int city_num, road_num;

int head[maxn];

map<string, int> city_name;

int city_cnt;

int edge_cnt;

int start_pos, end_pos;

int dist[maxn];

bool vis[maxn];



void addedge(int a, int b, int weight)

{

    edge[edge_cnt].v = b;

    edge[edge_cnt].w = weight;

    edge[edge_cnt].next = head[a];

    head[a] = edge_cnt++;

}



int city_id(char *st)

{

    string a;

    a.assign(st);

    if (city_name.find(a) == city_name.end())

    {

        city_name[a] = city_cnt++;

        return city_cnt - 1;

    }

    return city_name[a];

}



void input()

{

    memset(head, -1, sizeof(head));

    edge_cnt = 0;

    city_cnt = 0;

    city_name.clear();

    char a[maxl], b[maxl];

    int weight;

    for (int i = 0; i < road_num; i++)

    {

        scanf("%s%s%d", a, b, &weight);

        int id_a = city_id(a);

        int id_b = city_id(b);

        addedge(id_a, id_b, weight);

        addedge(id_b, id_a, weight);

    }

    scanf("%s%s", a, b);

    start_pos = city_id(a);

    end_pos = city_id(b);

}



int dijkstra(int s, int e)

{

    memset(vis, 0, sizeof(vis));

    memset(dist, 0, sizeof(dist));

    dist[s] = 10000;

    while (1)

    {

        int p = -1;

        int temp = -1;

        for (int i = 0; i < city_num; i++)

            if (!vis[i] && dist[i] > temp)

            {

                p = i;

                temp = dist[i];

            }

        if (p == -1)

            break;

        vis[p] = true;

        for (int i = head[p]; i != -1; i = edge[i].next)

            dist[edge[i].v] = max(dist[edge[i].v], min(dist[p], edge[i].w));

    }

    return dist[e];

}



int main()

{

    int t = 0;

    while (scanf("%d%d", &city_num, &road_num), city_num | road_num)

    {

        t++;

        input();

        printf("Scenario #%d\n%d tons\n\n", t, dijkstra(start_pos, end_pos));

    }

    return 0;

}

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