J 最大值

题目地址：

https://ac.nowcoder.com/acm/contest/5758/J

基本思路：

我们观察题目的意思，然后我们联想一下KMP中的next数组的定义，next数组是在当前位置前后缀相等的长度，其实和题目中要找的AC串是一个意思，因此在next数组中找最大就行了。

参考代码：

#pragma GCC optimize(2)
#pragma GCC optimize(3)
#include <bits/stdc++.h>
using namespace std;
#define IO std::ios::sync_with_stdio(false)
#define int long long
#define rep(i, l, r) for (int i = l; i <= r; i++)
#define per(i, l, r) for (int i = l; i >= r; i--)
#define mset(s, _) memset(s, _, sizeof(s))
#define pb push_back
#define pii pair <int, int>
#define mp(a, b) make_pair(a, b)
#define INF (int)1e18

inline int read() {
  int x = 0, neg = 1; char op = getchar();
  while (!isdigit(op)) { if (op == '-') neg = -1; op = getchar(); }
  while (isdigit(op)) { x = 10 * x + op - '0'; op = getchar(); }
  return neg * x;
}
inline void print(int x) {
  if (x < 0) { putchar('-'); x = -x; }
  if (x >= 10) print(x / 10);
  putchar(x % 10 + '0');
}

namespace KMP{
    vector<int> next;

    void build(const string &pattern){
      int n = pattern.length();
      next.resize(n + 1);
      for (int i = 0, j = next[0] = -1; i < n; next[++i] = ++j){
        while(~j && pattern[j] != pattern[i]) j = next[j];
      }
    }

    vector<int> match(const string &pattern, const string &text){
      vector<int> res;
      int n = pattern.length(), m = text.length();
      build(pattern);
      for (int i = 0, j = 0; i < m; ++i){
        while(j > 0 && text[i] != pattern[j]) j = next[j];
        if (text[i] == pattern[j]) ++j;
        if (j == n) res.push_back(i - n + 1), j = next[j];
      }
      return res;
    }
};

string str;
signed main() {
  IO;
  int t;
  cin >> t;
  while (t--){
    cin >> str;
    KMP::build(str);
    int ans = -1;
    for(auto it : KMP::next){
      ans = max(ans,it);
    }
    cout << ans << '\n';
  }
  return 0;
}