题意
求出最长的串长度，该串既是s1的前缀又是s2的后缀.
思路
把两个字符串连起来求一下前缀数组next[]即可~当然要用"#"或者其他非小写字母连接起来防止两个字符串真的混起来，比如s1="a",s2="aaaa"这种情况。
代码
[cpp]
#include <iostream>
#include <cstdio>
#include <cmath>
#include <algorithm>
#include <string>
#include <cstring>
#include <vector>
#include <set>
#include <stack>
#include <queue>
#define MID(x,y) ((x+y)/2)
#define MEM(a,b) memset(a,b,sizeof(a))
#define REP(i, begin, end) for (int i = begin; i <= end; i ++)
using namespace std;
typedef long long LL;
string s, s2;
int next[100005], len;
void get_next(){
len = s.size();
int j = -1;
next[0] = -1;
for (int i = 1; i < len; i ++){
while(j > -1 && s[i] != s[j+1]) j = next[j];
if (s[i] == s[j+1]) j ++;
next[i] = j;
}
}
int main(){
//freopen("test.in", "r", stdin);
//freopen("test.out", "w", stdout);
while(cin >> s){
cin >> s2;
s = s + "#" + s2;
//cout << s << endl;
get_next();
if (next[len-1] >= 0){
for (int i = 0; i <= next[len-1]; i ++){
cout << s[i];
}
cout << " ";
}
cout << next[len-1]+1 << endl;
}
return 0;
}
[/cpp]