这题主要有了中间的一些连通块的限制，不太好直接用二分图最大独立集做。考虑到图比较小，可以作补图求最大团来求解。
1 #include <iostream> 2 #include <vector> 3 #include <algorithm> 4 #include <string> 5 #include <string.h> 6 #include <stdio.h> 7 #include <queue> 8 #include <stack> 9 #include <map> 10 #include <set> 11 #include <cmath> 12 #include <ctime> 13 #include <cassert> 14 #include <sstream> 15 using namespace std; 16 17 const int N=110; 18 19 char s[N][N]; 20 int id[N][N]; 21 int dx[]={0,0,1,-1}; 22 int dy[]={1,-1,0,0}; 23 int n,m; 24 25 struct MC{ 26 bool graph[N][N]; 27 int stk[N][N],dp[N],mc; 28 int choice[N],vertex[N]; 29 void dfs(int n,int sz,int dep){ 30 if (sz==0){ 31 if (dep>mc){ 32 mc=dep; 33 for (int i=0;i<mc;i++) 34 vertex[i]=choice[i]; 35 } 36 return; 37 } 38 for (int i=0;i<sz;i++){ 39 int u=stk[dep][i]; 40 if (dep+dp[u]<=mc) return; 41 if (dep+sz-i<=mc) return; 42 choice[dep]=u; 43 int cnt=0; 44 for (int j=i+1;j<sz;j++){ 45 int v=stk[dep][j]; 46 if (graph[u][v]) 47 stk[dep+1][cnt++]=v; 48 } 49 dfs(n,cnt,dep+1); 50 } 51 } 52 int maxClique(int n){ 53 mc=1; 54 //节点从1开始标号 55 dp[n]=1; 56 for (int i=n-1;i>=1;i--){ 57 int sz=0; 58 for (int j=i+1;j<=n;j++) 59 if (graph[i][j]) 60 stk[1][sz++]=j; 61 choice[0]=i; 62 dfs(n,sz,1); 63 dp[i]=mc; 64 } 65 return mc; 66 } 67 void solve(int &cas) { 68 map<char,int> mp; 69 int cnt=0; 70 for (int i=1;i<=n;i++) { 71 for (int j=1;j<=m;j++) { 72 if (s[i][j]=='.') 73 id[i][j]=++cnt; 74 else if (mp.find(s[i][j])==mp.end()) 75 id[i][j]=mp[s[i][j]]=++cnt; 76 else 77 id[i][j]=mp[s[i][j]]; 78 } 79 } 80 //for (int i=1;i<=n;i++) for (int j=1;j<=m;j++) cout<<id[i][j]<<" ";cout<<endl; 81 for (int i=1;i<=cnt;i++) { 82 for (int j=1;j<=cnt;j++) { 83 if (i==j) graph[i][j]=false; 84 graph[i][j]=true; 85 } 86 } 87 for (int i=1;i<=n;i++) { 88 for (int j=1;j<=m;j++) { 89 int u=id[i][j]; 90 for (int k=0;k<4;k++) { 91 int ni=i+dx[k]; 92 int nj=j+dy[k]; 93 if (ni<=0||nj<=0||ni>n||nj>m) continue; 94 int v=id[ni][nj]; 95 graph[u][v]=false; 96 graph[v][u]=false; 97 } 98 } 99 } 100 printf("Case #%d: %d ",cas,maxClique(cnt)); 101 } 102 }mc; 103 104 int main () { 105 //freopen("out.txt","r",stdin); 106 int T; 107 scanf("%d",&T); 108 while (T--) { 109 scanf("%d %d",&n,&m); 110 for (int i=1;i<=n;i++) { 111 scanf("%s",s[i]+1); 112 } 113 static int cas=1; 114 mc.solve(cas); 115 cas++; 116 } 117 return 0; 118 }