【后缀数组】 POJ 3450 Corporate Identity

后缀数组+二分。。。思路很简单，把所有的串合并成一个串，串与串之间用不同的且从未出现过的单词隔开。。然后二分答案，找是否存在height数组连续大于等于当前二分的长度且分属于所有的串。。。。

#include <iostream>  #include <sstream>  #include <algorithm>  #include <vector>  #include <queue>  #include <stack>  #include <map>  #include <set>  #include <bitset>  #include <cstdio>  #include <cstring>  #include <cstdlib>  #include <cmath>  #include <climits>  #define maxn 800005#define eps 1e-6 #define mod 10007 #define INF 99999999  #define lowbit(x) (x&(-x))  //#define lson o<<1, L, mid  //#define rson o<<1 | 1, mid+1, R  typedef long long LL;using namespace std;char str[205];int s[maxn];int hash[maxn];int vis[4005];int sa[maxn], t[maxn], t2[maxn], c[maxn];int rank[maxn], height[maxn];int nn;int read(void){int n = 0, i, j, cnt = 50, len;for(i = 1; i <= nn; i++) {scanf("%s", str);len = strlen(str);for(j = 0; j < len; j++)hash[n] = i, s[n++] = str[j] - 'a' + 1;hash[n] = 0;s[n++] = cnt++;}s[n] = 0;return n;}void build(int n, int m){int i, k, p, *x = t, *y = t2;for(i = 0; i < m; i++) c[i] = 0;for(i = 0; i < n; i++) c[x[i] = s[i]]++;for(i = 1; i < m; i++) c[i] += c[i-1];for(i = n-1; i >= 0; i--) sa[--c[x[i]]] = i;for(k = 1; k <= n; k<<=1) {p = 0;for(i = n-k; i < n; i++) y[p++] = i;for(i = 0; i < n; i++) if(sa[i] >= k) y[p++] = sa[i] - k;for(i = 0; i < m; i++) c[i] = 0;for(i = 0; i < n; i++) c[x[y[i]]]++;for(i = 1; i < m; i++) c[i] += c[i-1];for(i = n-1; i >= 0; i--) sa[--c[x[y[i]]]] = y[i];swap(x, y), p = 1, x[sa[0]] = 0;for(i = 1; i < n; i++)x[sa[i]] = y[sa[i]] == y[sa[i-1]] && y[sa[i]+k] == y[sa[i-1]+k] ? p-1 : p++;if(p >= n) break;m = p;}}void getheight(int n){int i, j, k = 0;for(i = 0; i <= n; i++) rank[sa[i]] = i;for(i = 0; i < n; i++) {if(k) k--;j = sa[rank[i]-1];while(s[i+k] == s[j+k]) k++;height[rank[i]] = k;}}bool check(int len, int n){int cnt = 0, i;memset(vis, 0, sizeof vis);vis[0] = 1;for(i = 1; i <= n; i++) {if(height[i] >= len) {if(!vis[hash[sa[i-1]]]) vis[hash[sa[i-1]]] = 1, cnt++;if(!vis[hash[sa[i]]]) vis[hash[sa[i]]] = 1, cnt++;if(cnt >= nn) return 1;}else {memset(vis, 0, sizeof vis);vis[0] = 1;cnt = 0;}}return 0;}void search(int n){int bot = 0, top = strlen(str), mid, res = 0, cnt, i, j;while(top >= bot) {mid = (top+bot)>>1;if(check(mid, n)) bot = mid+1, res = mid;else top = mid-1;}if(res == 0) {printf("IDENTITY LOST\n");return;}memset(vis, 0, sizeof vis);vis[0] = 1, cnt = 0;for(i = 1; i <= n; i++) {if(height[i] >= res) {if(!vis[hash[sa[i-1]]]) vis[hash[sa[i-1]]] = 1, cnt++;if(!vis[hash[sa[i]]]) vis[hash[sa[i]]] = 1, cnt++;if(cnt >= nn) break;}else {memset(vis, 0, sizeof vis);vis[0] = 1;cnt = 0;}}for(j = sa[i]; j < sa[i]+res; j++)printf("%c", s[j]+'a'-1);printf("\n");}void debug(int n){int i;for(i = 1; i <= n; i++)printf("%d\n", height[i]);}int main(void){int n;while(scanf("%d", &nn), nn!=0) {n = read();build(n+1, 4100);getheight(n);search(n);}return 0;}