uestc 方老师分身 I

题意有点晕啊。。 水题一道。。

分身去教室的时候是单向的，回来的时候也是单向的，这时候就要反过来跑一遍最短路了。。

Dijkstra看着模板写的。。sigh~ 要不是渣渣。。还是记不住。。

#include<iostream>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<string>
#include<queue>
#include<algorithm>
#include<map>
#include<iomanip>
#include<climits>
#include<string.h>
#include<cmath>
#include<stdlib.h>
#include<vector>
#define INF 1e7
#define MAXN 100010
#define maxn 1000010
#define Mod 1000007
#define N 1010
using namespace std;
typedef long long LL;

int n, m, x;
int G[N][N];
int d[N], d1[N], d2[N];
bool vis[N];

bool Dijkstra(int x, int* d)
{
    int i, j, pos, min;
    for (i = 1; i <= n; ++i)
        d[i] = G[x][i];
    d[x] = 0;
    vis[x] = true;
    for (i = 1; i <= n; ++i) {
        min = INF;
        for (j = 1; j <= n; ++j) {
            if (d[j] < min && !vis[j]) {
                pos = j;
                min = d[j];
            }
        }
        if (min == INF) return false;
        vis[pos] = true;
        for (j = 1; j <= n; ++j)
            if (d[pos] + G[pos][j] < d[j] && !vis[j])
                d[j] = d[pos] + G[pos][j];
    }
    return true;
}

void process()
{
    int u, v, t;
    for (int i = 0; i <= n; ++i)
        for (int j = 0; j <= n; ++j)
            G[i][j] = INF;
    for (int i = 0; i < m; ++i) {
        cin >> u >> v >> t;
        G[u][v] = t;
    }
    memset(vis, 0, sizeof(vis));
    Dijkstra(x, d1);
    for (int i = 0; i <= n; ++i)
        for (int j = i + 1; j <= n; ++j)
            swap(G[i][j], G[j][i]);
    memset(vis, 0, sizeof(vis));
    Dijkstra(x, d2);
    for (int i = 0; i <= n; ++i)
        d[i] = d1[i] + d2[i];
    /*for (int i = 1; i <= n; ++i)
        cout << d[i] << " ";
    cout << endl;*/
    int ans = 0;
    for (int i = 1; i <= n; ++i)
            ans = max(ans, d[i]);
    cout << ans << endl;
}

int main()
{
    while (cin >> n >> m >> x)
        process();
    return 0;
}