bzoj 1266: [AHOI2006]上学路线route

思路：找出最短路图， 然后求最小割。

#include<bits/stdc++.h>
#define LL long long
 
using namespace std;
 
const int N = 507;
const int M = 124750;
const int inf = 0x3f3f3f3f;
 
struct Edge {
    int u, v, t, c, nx;
} edge[2][M << 1];
 
int n, m, S, T, tot[2], head[2][N], d[N], in[N], level[N];
 
void add(int x, int u, int v, int t, int c) {
    edge[x][tot[x]].u = u;
    edge[x][tot[x]].v = v;
    edge[x][tot[x]].t = t;
    edge[x][tot[x]].c = c;
    edge[x][tot[x]].nx = head[x][u];
    head[x][u] = tot[x]++;
}
 
void spfa() {
    queue<int> que;
    d[1] = 0; que.push(1); in[1] = 1;
    while(!que.empty()) {
        int u = que.front(); que.pop();
        for(int i = head[0][u]; ~i; i = edge[0][i].nx) {
            int v = edge[0][i].v, t = edge[0][i].t;
            if(d[u] + t < d[v]) {
                d[v] = d[u] + t;
                if(!in[v]) que.push(v);
            }
        }
        in[u] = 0;
    }
}
 
bool bfs() {
    memset(level, 0, sizeof(level));
    queue<int> que;
    que.push(S); level[S] = 1;
    while(!que.empty()) {
        int u = que.front(); que.pop();
        if(u == T) return true;
        for(int i = head[1][u]; ~i; i = edge[1][i].nx) {
            int v = edge[1][i].v;
            if(!level[v] && edge[1][i].c > 0) {
                que.push(v);
                level[v] = level[u] + 1;
            }
        }
    }
    return false;
}
 
int dfs(int u, int p) {
    if(u == T) return p;
    int ret = 0;
    for(int i = head[1][u]; ~i; i = edge[1][i].nx) {
        int v = edge[1][i].v, c = edge[1][i].c;
        if(c <= 0 || level[v] != level[u] + 1) continue;
        int f = dfs(v, min(p - ret, c));
        ret += f;
        edge[1][i].c -= f;
        edge[1][i ^ 1].c += f;
        if(ret == p) break;
    }
    if(!ret) level[u] = 1;
    return ret;
}
 
int Dinic() {
    int ans = 0;
    while(bfs()) ans += dfs(S, inf);
    return ans;
}
int main() {
    memset(head, -1, sizeof(head));
    memset(d, inf, sizeof(d));
    scanf("%d%d", &n, &m);
    S = 1, T = n;
    for(int i = 1; i <= m; i++) {
        int u, v, t, c;
        scanf("%d%d%d%d", &u, &v, &t, &c);
        add(0, u, v, t, c);
        add(0, v, u, t, c);
    }
 
    spfa();
 
    for(int i = 0; i < tot[0]; i++) {
        int u = edge[0][i].u;
        int v = edge[0][i].v;
        int t = edge[0][i].t;
        int c = edge[0][i].c;
 
        if(d[u] + t == d[v]) {
            add(1, u, v, t, c);
            add(1, v, u, t, 0);
        }
    }
 
    int ans = Dinic();
 
    printf("%d
", d[n]);
    printf("%d
", ans);
    return 0;
}