Bzoj3140:[Hnoi2013]消毒:二分图

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题目连接：3140:[Hnoi2013]消毒

首先如果只是两维的平面我们直接二分图覆盖集

那么三维的话枚举在x上枚举哪些层直接消去

剩下的同二维做法

#include<cstdio>#include<cstdlib>#include<iostream>#include<algorithm>using namespace std;const int maxn=5111;int n,m,tot=0,h[maxn],cnt=0,a,b,c;struct edge{int to,next;}G[maxn];struct point{int x,y,z;point(){}point(int _x,int _y,int _z){x=_x,y=_y,z=_z;if (b<=a&&b<=c) swap(x,y);else if (c<=a&&c<=b) swap(x,z);}}p[maxn];int tim=0,vis[maxn],girl[maxn],ans;bool mark[maxn];void add(int x,int y){G[++tot].to=y;G[tot].next=h[x];h[x]=tot;}bool find(int x){for (int i=h[x];i;i=G[i].next){int v=G[i].to;if (vis[v]==tim) continue;vis[v]=tim;if (!girl[v]||find(girl[v])){girl[v]=x; return 1;}}return 0;}void solve(int now){for (int i=1;i<=max(b,c);++i) h[i]=0; tot=0;for (int i=1;i<=max(b,c);++i) girl[i]=0;for (int i=1;i<=cnt;++i) if (!mark[p[i].x]) add(p[i].y,p[i].z);for (int i=1;i<=b;++i){++tim; now+=find(i);if (now>=ans) return;}ans=now;}void work(){ans=a;for (int i=1;i<(1<<a);++i){for (int j=1;j<=18;++j) mark[j]=0;int sum=0;for (int j=1;j<=a;++j) if (i&(1<<(j-1))) mark[j]=1,sum++;if (sum>=ans) continue;solve(sum);}}int main(){int T; scanf("%d",&T);while (T--){scanf("%d%d%d",&a,&b,&c);cnt=0;for (int i=1;i<=a;++i)for (int j=1;j<=b;++j)for (int k=1;k<=c;++k){int x; scanf("%d",&x);if (x) p[++cnt]=(point){i,j,k};}if (b<=a&&b<=c) swap(a,b);else if (c<=a&&c<=b) swap(a,c); work();printf("%d\n",ans);}}

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