思路不难想,求出sa以后二分随便搞搞,和上一题比较像。细节卡死人。。。
注意是大于一半。。。一开始以为是至少一半疯狂wa。。。
然后现在还把用来对拍的程序卡掉了。。。
c++代码如下:
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/* code by Tgotp poj 3294 */ #include<algorithm> #include<cstdio> #include<cstring> #define rep(i,x,y) for(register int i = x ;i <= y; ++ i) #define repd(i,x,y) for(register int i = x ; i >= y; -- i) using namespace std; const int N = 1e5 + 500; char s[1011],S[N]; int len,x[N],y[N << 1],sa[N],buc[N],height[N],rank[N]; int n,pos[111],belong[N]; inline void clear() { rep(i,0,len - 1) S[i] = 0; memset(buc,0,sizeof buc); memset(x,0,sizeof x); len = 0; } inline void swap(int&x,int&y) { int t = x; x = y; y = t; } inline void SA() { int m = 455; rep(i,0,len - 1) ++buc[x[i]]; rep(i,1,m) buc[i] += buc[i - 1]; repd(i,len - 1,0) sa[--buc[x[i]]] = i; for(register int k = 1 ;k <= len; k <<= 1) { int p = 0; repd(i,len - 1,len - k) y[p++] = i; rep(i,0,len - 1) if(sa[i] >= k) y[p++] = sa[i] - k; rep(i,0,m) buc[i] = 0; rep(i,0,len - 1) ++buc[x[i]]; rep(i,1,m) buc[i] += buc[i - 1]; repd(i,len - 1,0) sa[--buc[x[y[i]]]] = y[i]; rep(i,0,len - 1) swap(x[i],y[i]); p = 1; x[sa[0]] = 0; rep(i,1,len - 1) if(y[sa[i]] == y[sa[i - 1]] && y[sa[i] + k] == y[sa[i - 1] + k]) x[sa[i]] = p - 1; else x[sa[i]] = p++; if(p == len) break; m = p; } int p = 0; rep(i,0,len - 1) rank[sa[i]] = i; rep(i,0,len - 1) { if(p) --p; if(rank[i] == 0) continue; int t = sa[rank[i] - 1]; while(t + p < len && i + p < len && S[t + p] == S[i + p] ) ++p; height[rank[i]] = p; } } inline bool check(int x) { rep(i,1,len - 1) { int l,r; l = i; while(height[l] < x && l < len) ++l; r = l; while(height[r] >= x && r < len) ++r; if(l == len) break; rep(k,1,n) pos[k] = -1; rep(k,l - 1,r - 1) pos[belong[sa[k]]] = sa[k]; int num = 0; rep(k,1,n) if(~pos[k]) ++num; if(num > n / 2) return true; i = r; } return false; } inline void solve() { clear(); rep(i,1,n) { scanf("%s",s); int Len = strlen(s); rep(j,0,Len - 1) x[j + len] = s[j] + 100,S[j + len] = s[j],belong[j + len] = i; x[len + Len] = i;S[len + Len] = i; belong[len + Len] = 0; len += Len + 1; } SA(); int l = 0,r = len - 1,mid,ans; while(l <= r ) { if(check(mid = l + r >> 1)) l = mid + 1,ans = mid; else r = mid - 1; } if(ans == 0) puts("?"); else { rep(i,1,len - 1) { int l,r; l = i; while(height[l] < ans && l < len) ++l; r = l; while(height[r] >= ans && r < len) ++r; if(l == len) break; rep(k,1,n) pos[k] = -1; rep(k,l - 1,r - 1) pos[belong[sa[k]]] = sa[k]; int num = 0; rep(k,1,n) if(~pos[k]) ++num; if(num > n / 2) { rep(k,0,ans - 1) printf("%c",S[sa[l - 1] + k]); puts(""); } i = r; } } puts(""); } int main() { // freopen("1.in","r",stdin); // freopen("my.out","w",stdout); while(scanf("%d",&n),n != 0) solve(); return 0; } |
数据生成代码:
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