HDU 1874 畅通工程续(最短路训练

因为数据比较小

所以flyod spfa dijkstra 多可以过

Floyd

#include <bits/stdc++.h>
using namespace std;
const int INF = 0x3f3f3f3f;
const int maxn = ;

int s[maxn][maxn];
int main (){
    int n,m;
    while(~scanf("%d %d",&n,&m) ){
        for(int i=;i<n;i++){
            for(int j=;j<n;j++){
                if(i != j)
                    s[i][j] = INF;
                else
                    s[i][j] = ;
            }
        }
        for(int i=;i<m;i++){
            int x,y,v; scanf("%d %d %d",&x,&y,&v);
            s[x][y] = min(s[x][y],v);
            s[y][x] = min(s[y][x],v);
        }
        for(int k=;k<n;k++)
            for(int i=;i<n;i++)
                for(int j=;j<n;j++)
                    s[i][j] = min(s[i][j],s[i][k]+s[k][j]);
        int x,y;
        scanf("%d %d",&x,&y);
        if(s[x][y] == INF)
            printf("-1\n");
        else
            printf("%d\n",s[x][y]);
    }
}

spfa

// Spfa 算法

#include <bits/stdc++.h>
using namespace std;
const int maxn = ;
const int INF = 0x3f3f3f3f;

vector <pair<int,int> >E[maxn];
int d[maxn],inq[maxn];//inq 代表的是是否in queue
int n,m;
void init(){
    for(int i=;i<maxn;i++) d[i] = INF;
    for(int i=;i<maxn;i++) inq[i] = ;
    for(int i=;i<maxn;i++) E[i].clear();
}
int main()
{
    while (~scanf("%d %d",&n,&m)){
        init();
        for(int i=;i<=m;i++){
            int x,y,v;
            scanf("%d %d %d",&x,&y,&v);
            E[x].push_back(make_pair(y,v));
            E[y].push_back(make_pair(x,v));
        }
        queue<int>Q;
        int s,e;
        scanf("%d %d",&s,&e);
        d[s] = ;
        inq[s] = ;//起点进队列
        Q.push( s );
        while (Q.size()){
            int now = Q.front();
            Q.pop(); inq[now] = ;//该点出队列
            for(int i=;i < E[now].size();i++){
                int y = E[now][i].first;
                int v = E[now][i].second;
                if(d[y] > d[now] + v )
                {
                    d[y] = d[now] + v;
                    if( inq[y] )//如果在队列
                        continue;
                    inq[y] = ;
                    Q.push(y);
                }
            }
        }
        if(d[e] == INF)
            printf("-1\n");
        else
            printf("%d\n",d[e]);

    }
    return ;
}

dijkstra  //待测试

#include <bits/stdc++.h>
using namespace std;
const int maxn = ;
const int INF = 0x3f3f3f3f;
int n,m;
vector<pair<int,int> > E[maxn];
int d[maxn];
void init(){
    for(int i=;i<maxn;i++)
        E[i].clear() ,d[i] = INF;
}
int main()
{
    while (~scanf("%d %d",&n,&m)){
        init();
        for(int i=;i<=m;i++){
            int x,y,v;
            scanf("%d%d%d",&x,&y,&v);
            E[x].push_back(make_pair(y,v));
            E[y].push_back(make_pair(x,v));
        }
        int s,e;//start end;
        scanf("%d %d",&s,&e);
        d[s] = ;
        int v = -;
        priority_queue<pair<int,int> > Q;
        Q.push(make_pair(-d[s],s));
        while ( !Q.empty() )
        {
            int now = Q.top().second;
            if( now == e)//相等就可以直接跳出了
                break;
            Q.pop();
            for(int i=;i < E[now].size();i++)
            {
                v = E[now][i].first;
                if(d[v] > d[now] + E[now][i].second )
                {
                    d[v] = d[now] + E[now][i].second;
                    Q.push(make_pair(-d[v],v));
                }
            }

        }
        if(d[e] == INF)
            printf("-1\n");
        else
            printf("%d\n",d[e]);
    }
    return ;
}