HDU Today HDU2112 (dijkstra, 优先队列)_dtuhdtyioigrru-优快云博客

本文链接：https://blog.youkuaiyun.com/Tw_light/article/details/105643500

本文详细介绍了HDU2112的解题思路，主要利用Dijkstra算法和优先队列进行求解。通过对问题的深入分析，阐述了如何构建图并应用这两种数据结构来找到最短路径。

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#include<iostream>
#include<algorithm>
#include<cstring>
#include<string>
#include<cstdio>
#include<map>
#include<queue>
using namespace std;
const int INF = 0x3f3f3f3f;
const int MAXN = 1e5 + 9;

int N;
string start, ende, s1, s2;
map<string, int> Name;
int num, t;

struct Edge
{
    int to, w, nxt;
}edge[MAXN * 2];
int head[MAXN], cnt;

void init()
{
    Name.clear(); num = 0;
    memset(head, -1, sizeof(head)); cnt = 0;
}
void addEdge(int u, int v, int w)
{
    edge[cnt].to = v;
    edge[cnt].w = w;
    edge[cnt].nxt = head[u];
    head[u] = cnt++;
}
struct node
{
    int nod, w;
    node(int _nod, int _w):nod(_nod), w(_w) {}
    bool operator < (const node &o) const
    {
        return w > o.w;
    }
};

int dis[MAXN], vis[MAXN];
int dijkstra()
{
    if(Name[start] == Name[ende]) return 0;

    memset(dis, INF, sizeof(dis)); dis[Name[start]] = 0;
    memset(vis, 0, sizeof(vis)); vis[Name[start]] = 1;
    priority_queue<node> q;
    q.push({Name[start], 0});
    while(!q.empty())
    {
        struct node now = q.top(); q.pop();
        int u = now.nod;
        vis[u] = 1;

        for(int i = head[u]; i != -1; i = edge[i].nxt)
        {
            int to = edge[i].to;
            if(!vis[to] && dis[to] > dis[u] + edge[i].w)
            {
                dis[to] = dis[u] + edge[i].w;
                q.push({to, dis[to]});
            }
        }
    }
    if(dis[Name[ende]] == INF) return -1;
    return dis[Name[ende]];
}
int main()
{
    while(scanf("%d", &N) == 1 && (N != -1))
    {
        init();
        cin >> start >> ende;
        Name[start] = ++num;  // num为车站标号
        Name[ende] = ++num;

        for(int i = 1; i <= N; i++)
        {
            cin >> s1 >> s2 >> t;
            if(!Name[s1]) Name[s1] = ++num;
            if(!Name[s2]) Name[s2] = ++num;

            addEdge(Name[s1], Name[s2], t);  // 加边
            addEdge(Name[s2], Name[s1], t);
        }
        int ans = dijkstra();
        printf("%d\n", ans);
    }
    return 0;
}