Tjoi2019 甲苯先生和大中锋的字符串 后缀自动机 + 差分

tjoi胆子好大，直接出了两道送分题......

都 9102 年了，还有省选出模板题QAQ......

Code:

#include <bits/stdc++.h>
#define setIO(s) freopen(s".in","r",stdin) 
#define maxn 200010 
using namespace std;
char str[maxn];
int n,C[maxn],rk[maxn],arr[maxn]; 
int dis[maxn],f[maxn],ch[maxn][30],last,tot,cnt[maxn]; 
void init() { last = tot = 1; }
void ins(int c){
    int np = ++tot, p = last; 
    last = np, dis[np] = dis[p] + 1; 
    while(p && !ch[p][c]) ch[p][c] = np, p = f[p]; 
    if(!p) f[np] = 1; 
    else {
        int q = ch[p][c]; 
        if(dis[q] == dis[p] + 1) f[np] = q; 
        else {
            int nq = ++tot; 
            dis[nq] = dis[p] + 1; 
            memcpy(ch[nq],ch[q],sizeof(ch[q]));      
            f[np] = nq, f[nq] = f[q], f[q] = nq;
            while(p && ch[p][c] == q) ch[p][c] = nq, p = f[p];  
        }
    }
    ++cnt[np]; 
}
void work()
{
    int k; 
    init(); 
    scanf("%s%d",str + 1,&k), n = strlen(str + 1);         
    for(int i = 1;i <= n; ++i)  ins(str[i] - 'a'); 
    for(int i = 1;i <= tot; ++i) ++C[dis[i]]; 
    for(int i = 1;i <= tot; ++i) C[i] += C[i - 1]; 
    for(int i = tot;i >= 1; --i) rk[C[dis[i]]--] = i; 
    for(int i = tot;i >= 1; --i) {
        int u = rk[i]; 
        cnt[f[u]] += cnt[u]; 
        if(cnt[u] == k) 
        {
            arr[dis[f[u]] + 1] += 1; 
            arr[dis[u] + 1] -= 1;          
        }
    }
    int ans = 0, p = 0; 
    for(int i = 1;i <= tot; ++i) {
        arr[i] += arr[i - 1]; 
        if(arr[i] >= p && arr[i] != 0) ans = i, p = arr[i]; 
    }
    if(ans == 0) 
        printf("-1
"); 
    else 
        printf("%d
",ans); 
    for(int i = 0;i <= tot; ++i) 
    {
        for(int j = 0;j < 30; ++j) ch[i][j] = 0; 
        cnt[i] = C[i] = arr[i] = 0; 
    } 
    last = tot = 0; 
}
int main()
{
    // setIO("input"); 
    int T; 
    scanf("%d",&T); 
    while(T--) work();
    return 0; 
}