UVA 1161 - Objective: Berlin（最大流）

#include <cstdio> #include <cstring> #include <algorithm> #include <iostream> #include <string> #include <vector> #include <stack> #include <bitset> #include <cstdlib> #include <cmath> #include <set> #include <list> #include <deque> #include <map> #include <queue> #define Max(a,b) ((a)>(b)?(a):(b)) #define Min(a,b) ((a)<(b)?(a):(b)) using namespace std; typedef long long ll; typedef long double ld; const double eps = 1e⑹; const double PI = acos(⑴); const int mod = 1000000000 + 7; const int INF = 0x3f3f3f3f; const int seed = 131; const ll INF64 = ll(1e18); const int maxn = 10000 + 10; int T,n,m; struct Edge { int from,to,cap,flow; }; bool operator < (const Edge& a,const Edge& b) { return a.from < b.from || (a.from == b.from && a.to < b.to); } struct Dinic { int n,m,s,t; // 结点数， 边数（包括反向弧）， 源点编号， 汇点编号 vector<Edge> edges; // 边表， edges[e]和edges[e^1]互为反向弧 vector<int> G[maxn]; // 邻接表，G[i][j]表示结点i的第j条边在e数组中的序号 bool vis[maxn]; // BFS使用 int d[maxn]; // 从出发点到i的距离 int cur[maxn]; // 当前弧指针 void init(int n) { for(int i = 0; i < n; i++) G[i].clear(); edges.clear(); } void AddEdge(int from,int to,int cap) { edges.push_back((Edge){from,0}); edges.push_back((Edge){to,from,0}); m = edges.size(); G[from].push_back(m⑵); G[to].push_back(m⑴); } bool BFS() { memset(vis,sizeof(vis)); queue<int> Q; Q.push(s); vis[s] = 1; d[s] = 0; while(!Q.empty()) { int x = Q.front(); Q.pop(); for(int i = 0; i < G[x].size(); i++) { Edge& e = edges[G[x][i]]; if(!vis[e.to] && e.cap > e.flow) { //只斟酌残量网络中的弧 vis[e.to] = 1; d[e.to] = d[x] + 1; Q.push(e.to); } } } return vis[t]; } int DFS(int x,int a) { if(x == t || a == 0) return a; int flow = 0,f; for(int& i = cur[x]; i < G[x].size(); i++) { //上次斟酌的弧 Edge& e = edges[G[x][i]]; if(d[x] + 1 == d[e.to] && (f = DFS(e.to,min(a,e.cap-e.flow))) > 0) { e.flow += f; edges[G[x][i]^1].flow -= f; flow += f; a -= f; if(a == 0) break; } } return flow; } int Maxflow(int s,int t) { this->s = s; this->t = t; int flow = 0; while(BFS()) { memset(cur,sizeof(cur)); flow += DFS(s,INF); } return flow; } }g; int u,v,c,kase = 0,t,num[maxn],t1[maxn],t2[maxn],a[maxn],b[maxn]; char s1[11],s2[11],s3[maxn][10],s4[maxn][10]; map<string,int> p; int main() { while(~scanf("%d",&n)) { scanf("%s",s1); p.clear(); scanf("%s",s2); kase = 0; p[s1] = ++kase; if(!p.count(s2)) p[s2] = ++kase; int start = p[s1],endd = p[s2]; scanf("%s%d",s1,&m); t = ((s1[0]-'0')*10+s1[1]-'0')*60+(s1[2]-'0')*10+s1[3]-'0'; for(int i = 1; i <= m; i++) { scanf("%s%s%d%s%s",s3[i],s4[i],&num[i],s2); t1[i] = ((s1[0]-'0')*10+s1[1]-'0')*60+(s1[2]-'0')*10+s1[3]-'0'; t2[i] = ((s2[0]-'0')*10+s2[1]-'0')*60+(s2[2]-'0')*10+s2[3]-'0'; if(!p.count(s3[i])) p[s3[i]] = ++kase; if(!p.count(s4[i])) p[s4[i]] = ++kase; a[i] = p[s3[i]]; b[i] = p[s4[i]]; } g.init(2*m + 5); int res = m; int src = 2*m + 1,stc = 2*m + 2; for(int i = 1; i <= m; i++) { int id1 = b[i]; int cur = a[i]; g.AddEdge(i,i+m,num[i]); if(start == cur) g.AddEdge(src,i,INF); if(id1 == endd && t2[i] <= t) g.AddEdge(m+i,stc,INF); for(int j = 1; j <= m; j++) { if(i == j) continue; int id2 = a[j]; if(id1 != id2) continue; if(t2[i] + 30 <= t1[j]) g.AddEdge(i+m,j,INF); } } printf("%dn",g.Maxflow(src,stc)); } return 0; }