【网络流】 HDU 3605 Escape 缩图
给跪了,好腻害的缩图。。
一个人能到达的m个星球缩成一个点(状态),
源点再与点连接 容量为这个状态的出现的个数
再将点与可到达的星球连接 容量为状态的出现的个数
然后是星球与汇点连接 容量为输入的最后一行
#include <stdio.h> #include <string.h> #include <stdlib.h> #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 = 2010; const int MAXM = 41100; const int INF = 0x3f3f3f3f; 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 main() { //IN; int n,m,mp[2025]; while(scanf("%d%d",&n,&m)!=EOF) { init(); cler(mp,0); for(int i=1;i<=n;i++) { int sum=0; for(int j=0;j<m;j++) { int a; scanf("%d",&a); if(a) sum+=1<<j; } mp[sum]++; } for(int i=1<<m;i<(1<<m)+m;i++) { int a; scanf("%d",&a); addedge(i,m+(1<<m),a); } for(int i=1;i<(1<<m);i++) { if(mp[i]) { addedge(0,i,mp[i]); for(int j=0;j<m;j++) if((1<<j)&i) addedge(i,(1<<m)+j,mp[i]); } } if(n==sap(0,(1<<m)+m,(1<<m)+m+1)) puts("YES"); else puts("NO"); } return 0; }