【UVa1252】
1 // UVa1252 Twenty Questions 2 // Rujia Liu 3 #include<cstdio> 4 #include<ctime> 5 #include<cstring> 6 #include<algorithm> 7 #include<cassert> 8 using namespace std; 9 10 const int maxn = 128; 11 const int maxm = 11; 12 13 int kase, n, m; 14 char objects[maxn][maxm + 100]; 15 16 int vis[1<<maxm][1<<maxm], d[1<<maxm][1<<maxm]; 17 int cnt[1<<maxm][1<<maxm]; // cnt[s][a]: how many object satisfies: Intersect(featureSet(i), s) = a 18 19 // s: the set of features we already asked 20 // a: subset of s that the object has 21 int dp(int s, int a) { 22 if(cnt[s][a] <= 1) return 0; 23 if(cnt[s][a] == 2) return 1; 24 25 int& ans = d[s][a]; 26 if(vis[s][a] == kase) return ans; 27 vis[s][a] = kase; 28 29 ans = m; 30 for(int k = 0; k < m; k++) 31 if(!(s & (1<<k))) { // haven't asked 32 int s2 = s|(1<<k), a2 = a|(1<<k); 33 if(cnt[s2][a2] >= 1 && cnt[s2][a] >= 1) { 34 int need = max(dp(s2, a2), // the object has feature k 35 dp(s2, a)) + 1; // the object doesn't have feature k 36 ans = min(ans, need); 37 } 38 } 39 return ans; 40 } 41 42 void init() { 43 for(int s = 0; s < (1<<m); s++) { 44 for(int a = s; a; a = (a-1)&s) 45 cnt[s][a] = 0; 46 cnt[s][0] = 0; 47 } 48 for(int i = 0; i < n; i++) { 49 int features = 0; 50 for(int f = 0; f < m; f++) 51 if(objects[i][f] == '1') features |= (1<<f); 52 for(int s = 0; s < (1<<m); s++) 53 cnt[s][s & features]++; 54 } 55 } 56 57 58 int main() { 59 memset(vis, 0, sizeof(vis)); 60 while(scanf("%d%d", &m, &n) == 2 && n) { 61 ++kase; 62 for(int i = 0; i < n; i++) scanf("%s", objects[i]); 63 init(); 64 printf("%d ", dp(0, 0)); 65 } 66 return 0; 67 }