[BZOJ1717][Usaco2006 Dec]Milk Patterns 产奶的模式

#include <cstdio>
#include <algorithm>
using namespace std;
const int maxn = 20000 + 10;
int n, m, k, s[maxn];
int *p[maxn], cnt, last;
class cmp1{
    public:
        bool operator () (int *a, int *b){
            return *a < *b;
        }
};
int tax[maxn], tp[maxn], sa[maxn], rank[maxn], height[maxn];
inline bool cmp(int *r, int x, int y, int l){
    return r[x] == r[y] && r[x + l] == r[y + l];
}
inline void rsort(){
    for(int i = 0; i <= m; i++) tax[i] = 0;
    for(int i = 1; i <= n; i++) tax[rank[tp[i]]]++;
    for(int i = 1; i <= m; i++) tax[i] += tax[i - 1];
    for(int i = n; i; i--) sa[tax[rank[tp[i]]]--] = tp[i];
}
void suffix(){
    for(int i = 1; i <= n; i++){
        rank[i] = s[i];
        tp[i] = i;
    }
    m = n;
    rsort();
    for(int p, w = 1; w < n; w <<= 1, m = p){
        p = 0;
        for(int i = n - w + 1; i <= n; i++) tp[++p] = i;
        for(int i = 1; i <= n; i++) if(sa[i] > w) tp[++p] = sa[i] - w;
        rsort();
        swap(rank, tp);
        p = rank[sa[1]] = 1;
        for(int i = 2; i <= n; i++)
            rank[sa[i]] = cmp(tp, sa[i - 1], sa[i], w) ? p : ++p; 
    }
    for(int i = 1, j, k = 0; i <= n; height[rank[i++]] = k)
        for(k ? k-- : 0, j = sa[rank[i] - 1]; s[i + k] == s[j + k]; k++);
}
inline bool Judge(int mid){
    int tot = 0;
    for(int i = 1; i <= n; i++)
        if(height[i] >= mid){
            tot++;
            if(tot == k - 1) return true;
        }
        else tot = 0;
    return false;
}
int main(){
    scanf("%d %d", &n, &k);
    for(int i = 1; i <= n; i++)    scanf("%d", p[i] = s + i);
    sort(p + 1, p + n + 1, cmp1());
    last = *p[1];
    *p[1] = cnt = 1;
    for(int i = 2; i <= n; i++){
        if(*p[i] != last) cnt++;
        last = *p[i];
        *p[i] = cnt;
    }
    suffix();
    int l = 1, r = n, mid, ans;
    while(l <= r){
        mid = l + r >> 1;
        if(Judge(mid)){
            ans = mid;
            l = mid + 1;
        }
        else r = mid - 1;
    }
    printf("%d\n", ans);
    return 0;
}