bzoj1880: [Sdoi2009]Elaxia的路线

#include <cstdio>
#include <vector>
#include <cstring>
#include <iostream>
#include <algorithm>
#include <queue>

using namespace std;

const int maxn = 1510,inf = 1e9;

struct node
{
    int u, v, w;
};

int n, m, x1, y1, x2, y2,ans,rudu[maxn],d[maxn],dx1[maxn],dx2[maxn],dy1[maxn],dy2[maxn],vis[maxn];
vector <int> g1[maxn];
vector <node> e, g2[maxn];

void add1(int u, int v, int w)
{
    node temp;
    temp.u = u;
    temp.v = v;
    temp.w = w;
    e.push_back(temp);
    g1[u].push_back((int)e.size() - 1);
}

void add2(int u, int v, int w)
{
    node temp;
    temp.u = u;
    temp.v = v;
    temp.w = w;
    g2[u].push_back(temp);
    rudu[v]++;
}

void spfa(int s, int *d)
{
    memset(vis, 0, sizeof(vis));
    for (int i = 1; i <= n; i++)
        d[i] = inf;
    queue <int> q;
    d[s] = 0;
    vis[s] = 1;
    q.push(s);
    while (!q.empty())
    {
        int u = q.front();
        q.pop();
        vis[u] = 0;
        for (int i = 0; i < g1[u].size(); i++)
        {
            node temp = e[g1[u][i]];
            int v = temp.v;
            if (d[v] > d[u] + temp.w)
            {
                d[v] = d[u] + temp.w;
                if (!vis[v])
                {
                    vis[v] = 1;
                    q.push(v);
                }
            }
        }
    }
}

void topo()
{
    queue <int> q;
    for (int i = 1; i <= n; i++)
        if (!rudu[i])
            q.push(i);
    while (!q.empty())
    {
        int u = q.front();
        q.pop();
        for (int i = 0; i < g2[u].size(); i++)
        {
            int v = g2[u][i].v;
            if (d[v] < d[u] + g2[u][i].w)
            {
                d[v] = d[u] + g2[u][i].w;
                ans = max(ans, d[v]);
            }
            if (!(--rudu[v]))
                q.push(v);
        }
    }
}

int main()
{
    scanf("%d%d%d%d%d%d", &n, &m, &x1, &y1, &x2, &y2);
    for (int i = 1; i <= m; i++)
    {
        int u, v, w;
        scanf("%d%d%d", &u, &v, &w);
        add1(u, v, w);
        add1(v, u, w);
    }
    spfa(x1, dx1);
    spfa(x2, dx2);
    spfa(y1, dy1);
    spfa(y2, dy2);
    for (int i = 0; i < e.size(); i++)
    {
        int u = e[i].u, v = e[i].v, w = e[i].w;
        int len1 = min(dx1[u], dx1[v]) + min(dy1[u], dy1[v]) + w;
        int len2 = min(dx2[u], dx2[v]) + min(dy2[u], dy2[v]) + w;
        if (len1 == dx1[y1] && len2 == dx2[y2])
        {
            if (dx1[u] < dx1[v])
                add2(u, v, w);
            else
                add2(v, u, w);
        }
    }
    topo();
    printf("%d", ans);

    return 0;
}