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最新推荐文章于 2025-11-25 12:12:47 发布

原创最新推荐文章于 2025-11-25 12:12:47 发布 · 264 阅读

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本文介绍了一种使用邻接表与SPFA算法解决无向图中两点间最短路径问题的方法。通过实例展示了算法的具体实现过程，包括读取输入、建立图结构及执行SPFA算法等步骤。

//最短路，这里使用邻接表+spfa，图是无向的
#include <cstdio>
#include <cstring>
#include <queue>
#include <algorithm>
using namespace std;

#define MAXN    1001
#define MAXM    10001
#define INF     0x3f3f3f3f

struct Edge{
        int v, w, next;
}edge[MAXM];

int head[MAXN], dis[MAXN], used[MAXN];
int e_cnt, want_list[MAXN], near_list[MAXN];

void insert_arc(int u, int v, int w)
{
        edge[e_cnt].v = v; edge[e_cnt].w = w;
        edge[e_cnt].next = head[u]; head[u] = e_cnt ++;
        swap(u, v);
        edge[e_cnt].v = v; edge[e_cnt].w = w;
        edge[e_cnt].next = head[u]; head[u] = e_cnt ++;
}

int spfa(int src, int des)
{
        int u, v;
        queue<int> q;
        fill(dis, dis+MAXN, INF);
        memset(used, 0, sizeof(used));
        dis[src] = 0; used[src] = 1; q.push(src);
        while( !q.empty() ) {
                u = q.front(); q.pop(); used[u] = 0;
                for(int i = head[u]; -1 != i; i = edge[i].next) {
                        v = edge[i].v;
                        if( dis[v] < dis[u]+edge[i].w ) {
                                continue;
                        }
                        if( !used[v] ) {
                                q.push(v);
                        }
                        dis[v] = dis[u]+edge[i].w;
                }
        }
        return dis[des];
}

int main(int argc, char const *argv[])
{
#ifndef ONLINE_JUDGE
        freopen("test.in", "r", stdin);
#endif
        int road_cnt, near_cnt, want_cnt, u, v, w, ans;
        while( ~scanf("%d %d %d", &road_cnt, &near_cnt, &want_cnt) ) {
                e_cnt = 0; memset(head, -1, sizeof(head));
                for(int i = 0; i < road_cnt; i ++) {
                        scanf("%d %d %d", &u, &v, &w);
                        insert_arc(u, v, w);
                }
                for(int i = 0;  i < near_cnt; i ++) {
                        scanf("%d", &near_list[i]);
                }
                for(int i = 0;  i < want_cnt; i ++) {
                        scanf("%d", &want_list[i]);
                }
                ans = INF;
                for(int i = 0; i < near_cnt; i ++) {
                        for(int j = 0; j < want_cnt; j ++) {
                                ans = min(ans, spfa(near_list[i], want_list[j]));
                        }
                }
                printf("%d\n", ans);
        }
        return 0;
}