【网络流】 HDU 4309 Seikimatsu Occult Tonneru 状压枚举边
题意:有三种类型的路
类型 1. 从 U 到 V 能走INF个人 能躲 d 个人
类型 2. 从 U 到 V 能走INF 个人 不能 躲人
类型 3. 从 U 到 V 能走INF 个人 要用该路时需要花费一定费用
要求能躲最多人 且花费最少
类型3 的路最多有 12 条
所以我们用二进制 枚举 类型3
(也有递归来枚举,dfs心太累)
#include <cstdio> #include <cstring> #include <cstdlib> #include <string> #include <iostream> #include <algorithm> #include <sstream> #include <cmath> using namespace std; #include <queue> #include <stack> #include <vector> #include <deque> #include <set> #include <map> #include <time.h>; #define cler(arr, val) memset(arr, val, sizeof(arr)) #define FOR(i,a,b) for(int i=a;i<=b;i++) #define IN freopen ("in.txt" , "r" , stdin); #define OUT freopen ("out.txt" , "w" , stdout); typedef long long LL; const int MAXN = 200; const int MAXM = 100000; const int INF = 0x3f3f3f3f; //const int INF = 922222; const int mod = 1000000007; struct Edge { int to,next,cap,flow; } edge[MAXM]; //注意是MAXM int tol; int head[MAXN]; int gap[MAXN],dep[MAXN],cur[MAXN]; void init() { tol = 0; memset(head,-1,sizeof (head)); } void addedge (int u,int v,int w,int rw = 0) { edge[tol].to = v; edge[tol].cap = w; edge[tol].flow = 0; edge[tol].next = head[u]; head[u] = tol++; edge[tol].to = u; edge[tol].cap = rw; edge[tol].flow = 0; edge[tol].next = head[v]; head[v] = tol++; } int Q[MAXN]; void BFS(int start,int end) { memset(dep,-1,sizeof(dep)); memset(gap,0,sizeof(gap)); gap[0] = 1; int front = 0, rear = 0; dep[end] = 0; Q[rear++] = end; while(front != rear) { int u = Q[front++]; for(int i = head[u]; i != -1; i = edge[i].next) { int v = edge[i]. to; if(dep[v] != -1)continue; Q[rear++] = v; dep[v] = dep[u] + 1; gap[dep[v]]++; } } } int S[MAXN]; int sap(int start,int end, int N) { BFS(start,end); memcpy(cur,head,sizeof(head)); int top = 0; int u = start; int ans = 0; int i; while(dep[start] < N) { if(u == end) { int Min = INF; int inser; for( i = 0; i < top; i++) { if(Min > edge[S[i]].cap - edge[S[i]].flow) { Min = edge[S[i]].cap - edge[S[i]].flow; inser = i; } } for( i = 0; i < top; i++) { edge[S[i]]. flow += Min; edge[S[i]^1].flow -= Min; } ans += Min; top = inser; u = edge[S[top]^1].to; continue; } bool flag = false; int v; for( i = cur[u]; i != -1; i = edge[i]. next) { v = edge[i]. to; if(edge[i].cap - edge[i].flow && dep[v]+1 == dep[u]) { flag = true; cur[u] = i; break; } } if(flag) { S[top++] = cur[u]; u = v; continue; } int Min = N; for( i = head[u]; i != -1; i = edge[i].next) { if(edge[i].cap - edge[i].flow && dep[edge[i].to] < Min) { Min = dep[edge[i].to]; cur[u] = i; } } gap[dep[u]]--; if(!gap[dep[u]]) return ans; dep[u] = Min + 1; gap[dep[u]]++; if(u != start)u = edge[S[--top]^1].to; } return ans; } int u[MAXM],v[MAXM],d[MAXM],p[MAXM],man[MAXN]; int main() { #ifndef ONLINE_JUDGE freopen("in.txt", "r", stdin); // freopen("out.txt", "w", stdout); #endif int n,m; while(scanf("%d%d",&n,&m)!=EOF) { int star=0,end=n+1,mansum,num3=0,num1=0; for(int i=1;i<=n;i++) { scanf("%d",&man[i]); if(d!=0) mansum+=man[i]; } for(int i=0;i<m;i++) { scanf("%d%d%d%d",&u[i],&v[i],&d[i],&p[i]); if(p[i]<0&&d[i]!=0) num1++; else if(p[i]>0) num3++; } if(!num1)//优化了 下快了很多 { puts("Poor Heaven Empire"); continue; } int maxflow=0,cost=0; for(int k=0;k<(1<<num3);k++)//枚举类型3 { init(); int x=end,cc=0,cos=0,ans; for(int i=1;i<=n;i++) addedge(star,i,man[i]); for(int i=0;i<m;i++) { if(p[i]<0) { addedge(u[i],v[i],INF); addedge(u[i],end,d[i]); } else if(p[i]==0) { addedge(u[i],v[i],INF); } else if(p[i]>0) { if(k&(1<<cc)) { addedge(u[i],v[i],INF); cos+=d[i]; } else addedge(u[i],v[i],1); cc++; } } ans=sap(star,end,n+2); if(ans>maxflow) maxflow=ans,cost=cos; else if(ans==maxflow&&cost>cos) cost=cos; } if(maxflow==0) puts("Poor Heaven Empire"); else printf("%d %d\n",maxflow,cost); } return 0; }
所以我们用二进制 枚举 类型3