LOJ#3103. 「JSOI2019」节日庆典

能当最小位置的值一定是一个最小后缀，而有用的最小后缀不超过\(\log n\)个

为什么不超过\(\log n\)个，看了一下zsy的博客。。

假如\(i = AAB\)，\(j = AB\)，\(B\)是\(A\)的一个严格前缀，\(|j| < |i| < 2|j|\)

但是有\(k = B\)，导致了若\(j\)比\(i\)优，则\(k\)会比\(j\)优，\(j\)比\(k\)优，则\(i\)会比\(j\)优，那么\(j\)就没用了

然后取这\(\log\)里最大的就是一段后缀和开头比较，可以预处理出每个串和开头的lcp，用扩展kmp

#include <bits/stdc++.h>
#define fi first
#define se second
#define pii pair<int,int>
#define mp make_pair
#define pb push_back
#define space putchar(' ')
#define enter putchar('\n')
#define eps 1e-10
#define ba 47
#define MAXN 5005
//#define ivorysi
using namespace std;
typedef long long int64;
typedef unsigned int u32;
typedef double db;
template<class T>
void read(T &res) {res = 0;T f = 1;char c = getchar();while(c < '0' || c > '9') {if(c == '-') f = -1;c = getchar();}while(c >= '0' && c <= '9') {res = res * 10 +c - '0';c = getchar();}res *= f;
}
template<class T>
void out(T x) {if(x < 0) {x = -x;putchar('-');}if(x >= 10) {out(x / 10);}putchar('0' + x % 10);
}
char s[3000006];
int L,lcp[3000006];
bool cmp(int l0,int r0,int l1,int r1) {if(r0 < l0) return true;if(r1 < l1) return false;int l = min(lcp[l0],min(r1,r0 - l0 + 1));if(s[l0 + l] <= s[l1 + l]) return true;return false;
}
void Solve() {scanf("%s",s + 1);L = strlen(s + 1);lcp[1] = L;int p = 0,r = 0;for(int i = 2 ; i <= L ; ++i) {int t = 0;if(r >= i) t = min(r - i + 1,lcp[i - p + 1]);while(i + t <= L && s[t + 1] == s[i + t]) ++t;lcp[i] = t;if(r < i + t - 1) {p = i;r = i + t - 1;}}vector<int> f;f.clear();for(int i = 1 ; i <= L ; ++i) {vector<int> g;g.clear();g.pb(i);for(auto t : f) {while(g.size() && s[t + i - g.back()] < s[i]) g.pop_back();if(g.size() == 0 || s[t + i - g.back()] == s[i]) {while(g.size() && i - t + 1 <= 2 * (i - g.back() + 1)) g.pop_back();g.pb(t);}}f = g;int res = f[0];for(int j = 1 ; j < f.size() ; ++j) {if(cmp(f[j] + i - res + 1,res - 1,1,res - f[j] - 1)) res = f[j];}out(res);space;}enter;
}
int main(){
#ifdef ivorysifreopen("f1.in","r",stdin);
#endifSolve();
}