UVA 10000 Longest Paths(SPFA)

来源：互联网发布：电子贺卡制作软件编辑：程序博客网时间：2024/05/16 11:13

题意是让求最长路，和最短路思想一样
代码是套的kuangbin的SPFA的模板

#include <iostream>#include <vector>#include <queue>#include <cstring>using namespace std;const int MAXN = 110;struct Edge{    int v,cost;    Edge(int _v = 0, int _cost = 0):v(_v),cost(_cost){}};vector<Edge> E[MAXN];void addEdge(int u, int v, int w){    E[u].push_back(Edge(v,w));}bool vis[MAXN];bool cnt[MAXN];int dist[MAXN];bool SPFA(int start, int n){    memset(cnt,0,sizeof(cnt));    memset(vis,false,sizeof(vis));    memset(dist,0,sizeof(dist));    vis[start] = true;    dist[start] = 0;    queue<int> que;    que.push(start);    cnt[start] = 1;    while(!que.empty())    {        int u = que.front();        que.pop();        vis[u] = false;        for(int i = 0; i < E[u].size(); ++i)        {            int v = E[u][i].v;            if(dist[v] < dist[u] + E[u][i].cost)            {                dist[v] = dist[u] + E[u][i].cost;                if(!vis[v])                {                    vis[v] = true;                    que.push(v);                    if(++cnt[v] > n) return false;                }            }        }    }    return true;}int main(){    int n,start,time = 0;    while(cin >> n && n)    {        ++time;        memset(E,0,sizeof(E));        cin >> start;        int u,v;        while(cin >> u >> v && (u+v))            addEdge(u,v,1);        SPFA(start,n);        int res = 0,ires = 0;        for(int i = 1; i <= n; ++i)        {            if(dist[i] > res)            {                res = dist[i];                ires = i;            }        }        cout << "Case " << time << ": The longest path from " << start << " has length " << res << ", finishing at " << ires << "." << endl << endl;    }    return 0;}

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