BZOJ1266 [AHOI2006] 上学路线route

  1 #include <iostream>
  2 #include <cstdio>
  3 #include <algorithm>
  4 #include <cstring>
  5 #include <queue>
  6 #define rep(i,l,r) for(int i=l; i<=r; i++)
  7 #define clr(x,y) memset(x,y,sizeof(x))
  8 #define travel(x) for(Edge *p=last[x]; p; p=p->pre)
  9 typedef long long ll;
 10 using namespace std;
 11 const int INF = 0x3f3f3f3f;
 12 const int maxn = 510;
 13 struct Edge{
 14     Edge *pre,*rev; int to,cost;
 15 }edge[250010];
 16 Edge *last[maxn],*cur[maxn],*pt;
 17 int n,m,ans=0,a[124760],b[124760],c[124760],t[124760],d[2][maxn];
 18 bool isin[maxn];
 19 queue <int> q;
 20 inline int read(){
 21     int ans = 0, f = 1;
 22     char c = getchar();
 23     while (!isdigit(c)){
 24         if (c == ‘-‘) f = -1;
 25         c = getchar();
 26     }
 27     while (isdigit(c)){
 28         ans = ans * 10 + c - ‘0‘;
 29         c = getchar();
 30     }
 31     return ans * f;
 32 }
 33 inline void addedge(int x,int y,ll z){
 34     pt->pre = last[x]; pt->to = y; pt->cost = z; last[x] = pt++;
 35 }
 36 inline void add(int x,int y,ll z){
 37     addedge(x,y,z); addedge(y,x,0); last[x]->rev = last[y]; last[y]->rev = last[x];
 38 }
 39 void spfa(int x,int t){
 40     clr(d[t],INF); d[t][x] = 0;
 41     clr(isin,0); isin[x] = 1; q.push(x);
 42     while (!q.empty()){
 43         int now = q.front(); q.pop(); isin[now] = 0;
 44         travel(now){
 45             if (d[t][p->to] > d[t][now] + p->cost){
 46                 d[t][p->to] = d[t][now] + p->cost;
 47                 if (!isin[p->to]){
 48                     isin[p->to] = 1;
 49                     q.push(p->to);
 50                 }
 51             }
 52         }
 53     }
 54 }
 55 bool bfs(){
 56     while (!q.empty()) q.pop();
 57     clr(d[0],-1); d[0][1] = 0; q.push(1);
 58     while (!q.empty()){
 59         int now = q.front(); q.pop();
 60         travel(now){
 61             if (d[0][p->to] == -1 && p->cost > 0){
 62                 d[0][p->to] = d[0][now] + 1;
 63                 q.push(p->to);
 64                 if (p->to == n) return 1;
 65             }
 66         }
 67     }
 68     return 0;
 69 }
 70 int dfs(int x,int flow){
 71     if (x == n || (!flow)) return flow; int w = 0;
 72     for(Edge *p=cur[x]; p && w < flow; p=p->pre){
 73         if (d[0][p->to] == d[0][x] + 1 && p->cost > 0){
 74             int delta = dfs(p->to,min(p->cost,flow-w));
 75             p->cost -= delta;
 76             p->rev->cost += delta;
 77             w += delta;
 78             if (p->cost) cur[x] = p;
 79         }
 80     }
 81     if (w < flow) d[0][x] = -1;
 82     return w;
 83 }
 84 int main(){
 85     n = read(); m = read(); clr(last,0); pt = edge;
 86     rep(i,1,m){
 87         a[i] = read(); b[i] = read(); t[i] = read(); c[i] = read();
 88         addedge(a[i],b[i],t[i]); addedge(b[i],a[i],t[i]);
 89     }
 90     spfa(1,0); spfa(n,1);
 91     printf("%d\n",d[0][n]);
 92     clr(last,0); pt = edge;
 93     rep(i,1,m){
 94         if (d[0][a[i]] + t[i] + d[1][b[i]] == d[0][n]){
 95             add(a[i],b[i],c[i]);
 96         }
 97         if (d[0][b[i]] + t[i] + d[1][a[i]] == d[0][n]){
 98             add(b[i],a[i],c[i]);
 99         }
100     }
101     while (bfs()){
102         rep(i,1,n) cur[i] = last[i];
103         ans += dfs(1,INF);
104     }
105     printf("%d\n",ans);
106     return 0;
107 }