CF #244 D. Match & Catch 后缀数组

题目链接：http://codeforces.com/problemset/problem/427/D

大意是寻找两个字符串中最短的公共子串，要求子串在两个串中都是唯一的。

造一个S#T的串，做后缀数组，从小到大枚举子串长度在height数组中扫描，如果某一个组中来自两个串的数量分别为1，就找到了答案。

 #include <iostream>
 #include <vector>
 #include <algorithm>
 #include <string>
 #include <string.h>
 #include <stdio.h>
 #include <math.h>
 #include <stdlib.h>
 #include <queue>
 #include <stack>
 #include <map>
 #include <set>
 #include <ctime>
 #include <numeric>
 #include <cassert>

 using namespace std;

 const int N=;;

 char s[N];

 struct SuffixArray {
     int wa[N], wb[N], cnt[N], wv[N];
     int rk[N], height[N];
     int sa[N];
     bool cmp(int r[], int a, int b, int l) {
         return r[a] == r[b] && r[a+l] == r[b+l];
     }
     void calcSA(char r[], int n, int m) {
         int i, j, p, *x = wa, *y = wb;
         for (i = ; i < m; ++i) cnt[i] = ;
         for (i = ; i < n; ++i) cnt[x[i]=r[i]]++;
         for (i = ; i < m; ++i) cnt[i] += cnt[i-];
         for (i = n-; i >= ; --i) sa[--cnt[x[i]]] = i;
         for (j = , p = ; p < n; j *= , m = p) {
             for (p = , i = n - j; i < n; ++i) y[p++] = i;
             for (i = ; i < n; ++i) if (sa[i] >= j) y[p++] = sa[i] - j;
             for (i = ; i < n; ++i) wv[i] = x[y[i]];
             for (i = ; i < m; ++i) cnt[i] = ;
             for (i = ; i < n; ++i) cnt[wv[i]]++;
             for (i = ; i < m; ++i) cnt[i] += cnt[i-];
             for (i = n-; i >= ; --i) sa[--cnt[wv[i]]] = y[i];
             for (swap(x, y), p = , x[sa[]] = , i = ; i < n; ++i)
                 x[sa[i]] = cmp(y, sa[i-], sa[i], j) ? p- : p++;
         }
     }
     void calcHeight(char r[], int n) {
         int i, j, k = ;
         for (i = ; i <= n; ++i) rk[sa[i]] = i;
         for (i = ; i < n; height[rk[i++]] = k)
             for (k?k--:, j = sa[rk[i]-]; r[i+k] == r[j+k]; k++);
     }
     bool solve(int k,int n,int div) {
         int ca=,cb=;
         for (int i=;i<=n;i++) {
             if (height[i]<k) {
                 if (ca==&&cb==)
                     return true;
                 ca=;cb=;
                 if (sa[i]<div) ca++;
                 else if (sa[i]>div) cb++;
                 continue;
             }
             if (sa[i]<div) ca++;
             else if (sa[i]>div) cb++;
         }
         return ca==&&cb==;
     }
 }suf;

 char a[N],b[N];

 int main(){
     scanf("%s %s",a,b);
     int n=strlen(a),m=strlen(b);
     strcpy(s,a);
     s[n]='#';
     strcpy(s+n+,b);
     int tot=n+m+;
     suf.calcSA(s,tot+,);
     suf.calcHeight(s,tot);
     int ret=-;
     for (int i=;i<=n;i++) {
         if (suf.solve(i,tot,n)) {
             ret=i;
             break;
         }
     }
     printf("%d\n",ret);
     return ;
 }