题目:http://www.lydsy.com/JudgeOnline/problem.php?id=2756
对棋盘进行黑白染色。若答案为x,有c1*x-s1==c2*x-s2得x=(s1-s2)/(c1-c2),那么若c1!=c2,检测x就可以了。若不是就二分x。
建图:s->黑点 c=x-a[i][j] 白点->t c=x-a[i][j] 黑->白 c=inf
#include<cstring> #include<iostream> #include<algorithm> #include<cstdlib> #include<cstdio> #include<cmath> #include<queue> #define rep(i,l,r) for (int i=l;i<=r;i++) #define down(i,l,r) for (int i=l;i>=r;i--) #define clr(x,y) memset(x,y,sizeof(x)) #define maxn 2005 #define eps 1e-3 #define ll long long #define inf (1LL<<50) using namespace std; struct data{int obj,pre;ll c; }e[200500]; int dx[4]={0,1,0,-1},dy[4]={1,0,-1,0}; int head[maxn],cur[maxn],uu[maxn],n,m,t,tot,s; ll c1,c2,s1,s2,a[42][42]; ll read(){ ll x=0,f=1; char ch=getchar(); while (!isdigit(ch)) {if (ch==‘-‘) f=-1; ch=getchar();} while (isdigit(ch)) {x=x*10+ch-‘0‘; ch=getchar();} return x*f; } void insert(int x,int y,ll z){ e[++tot].obj=y; e[tot].c=z; e[tot].pre=head[x]; head[x]=tot; e[++tot].obj=x; e[tot].c=0; e[tot].pre=head[y]; head[y]=tot; } int p(int x,int y){ return (x-1)*m+y; } bool bfs(){ queue<int> q; q.push(0); clr(uu,-1); uu[0]=0; while (!q.empty()){ int u=q.front(); q.pop(); for (int j=head[u];j;j=e[j].pre){ int v=e[j].obj; if (uu[v]==-1&&e[j].c) { uu[v]=uu[u]+1; q.push(v); } } } if (uu[t]==-1) return 0; return 1; } ll dfs(int x,ll mx){ if (x==t) return mx; ll used=0; for (int j=cur[x];j;j=e[j].pre){ int v=e[j].obj; if (uu[v]==uu[x]+1){ ll w=dfs(v,min(e[j].c,mx-used)); e[j].c-=w; e[j^1].c+=w; used+=w; if (e[j].c) cur[x]=j; if (used==mx) return mx; } } if (!used) uu[x]=-1; return used; } ll dinic(){ ll ans=0; while (bfs()){ rep(i,0,t) cur[i]=head[i]; ans+=dfs(0,inf); } return ans; } bool jud(ll x){ tot=1; clr(head,0); s=0; t=n*m+1; ll cnt=0; rep(i,1,n) rep(j,1,m) { if ((i+j)&1) { insert(0,p(i,j),x-a[i][j]),cnt+=x-a[i][j]; rep(k,0,3) { int x=i+dx[k],y=j+dy[k]; if (x<1||x>n||y<1||y>m) continue; insert(p(i,j),p(x,y),inf); } } else insert(p(i,j),t,x-a[i][j]); } if (dinic()!=cnt) return 0; return 1; } int main(){ int T=read(); while (T--){ ll mx=0; c1=0,c2=0,s1=0,s2=0; n=read(); m=read(); rep(i,1,n) rep(j,1,m){ a[i][j]=read(); mx=max(mx,a[i][j]); if ((i+j)&1) c1++,s1+=a[i][j]; else c2++,s2+=a[i][j]; } if (c1!=c2){ ll x=(s1-s2)/(c1-c2); if (x>=mx) if (jud(x)) {printf("%lld\n",x*c1-s1); continue;} puts("-1"); } else { ll l=mx,r=inf; while (l<=r){ ll mid=(l+r)/2; if (jud(mid)) r=mid-1; else l=mid+1; } printf("%lld\n",l*c1-s1); } } return 0; }
时间: 2024-10-05 20:45:06