【后缀数组】 HDOJ 5030 Rabbit's String

#include <iostream>
#include <queue>
#include <stack>
#include <map>
#include <set>
#include <bitset>
#include <cstdio>
#include <algorithm>
#include <cstring>
#include <climits>
#include <cstdlib>
#include <cmath>
#include <time.h>
#define maxn 100005
#define maxm 300005
#define eps 1e-10
#define mod 10000007
#define INF 1e9
#define lowbit(x) (x&(-x))
#define mp make_pair
#define ls o<<1
#define rs o<<1 | 1
#define lson o<<1, L, mid
#define rson o<<1 | 1, mid+1, R
typedef long long LL;
//typedef int LL;
using namespace std;
LL qpow(LL a, LL b){LL res=1,base=a;while(b){if(b%2)res=res*base;base=base*base;b/=2;}return res;}
LL powmod(LL a, LL b){LL res=1,base=a;while(b){if(b%2)res=res*base%mod;base=base*base%mod;b/=2;}return res;}
void scanf(int &__x){__x=0;char __ch=getchar();while(__ch==' '||__ch=='\n')__ch=getchar();while(__ch>='0'&&__ch<='9')__x=__x*10+__ch-'0',__ch = getchar();}
LL gcd(LL _a, LL _b){if(!_b) return _a;else return gcd(_b, _a%_b);}
//head

char s[maxn];
int sa[maxn], c[maxn], t1[maxn], t2[maxn];
int height[maxn], rank[maxn];

void build(int n, int m)
{
int *x = t1, *y = t2, p;
for(int i = 0; i < m; i++) c[i] = 0;
for(int i = 0; i < n; i++) c[x[i] = s[i]]++;
for(int i = 1; i < m; i++) c[i] += c[i-1];
for(int i = n-1; i >= 0; i--) sa[--c[x[i]]] = i;
for(int k = 1; k <= n; k <<= 1) {
p = 0;
for(int i = n - k; i < n; i++) y[p++] = i;
for(int i = 0; i < n; i++) if(sa[i] >= k) y[p++] = sa[i] - k;
for(int i = 0; i < m; i++) c[i] = 0;
for(int i = 0; i < n; i++) c[x[y[i]]]++;
for(int i = 1; i < m; i++) c[i] += c[i-1];
for(int i = n-1; i >= 0; i--) sa[--c[x[y[i]]]] = y[i];
p = 1, swap(x, y), x[sa[0]] = 0;
for(int i = 1; i < n; i++)
x[sa[i]] = y[sa[i]] == y[sa[i-1]] && y[sa[i]+k] == y[sa[i-1]+k] ? p-1 : p++;
if(p >= n) break;
m = p;
}
}

void getheight(int n)
{
int k = 0;
for(int i = 0; i <= n; i++) rank[sa[i]] = i;
for(int i = 0; i < n; i++) {
if(k) k--;
int j = sa[rank[i] - 1];
while(s[i+k] == s[j+k]) k++;
height[rank[i]] = k;
}
}

int kk, cnt1, cnt2;
LL sum[maxn];
pair<int, int> p1[maxn], p2[maxn];

int cmp(pair<int, int> a, pair<int, int> b) {return a.first < b.first;}

int calc(void)
{
sort(p1, p1+cnt1, cmp);
int t = INF, res = 0;
for(int i = cnt1-1; i >= 0; i--) {
if(p1[i].second >= t) continue;
t = p1[i].second;
p2[cnt2++] = p1[i];
}
sort(p2, p2+cnt2, cmp);
t = -1;
for(int i = 0; i < cnt2; i++) {
if(p2[i].first <= t) continue;
res++;
t = p2[i].second;
}
return res;
}

bool check(LL now, int n)
{
int t = lower_bound(sum+1, sum+n+1, now) - sum;
int ans = sa[t];
int len = now - sum[t - 1] + height[t];
cnt1 = cnt2 = 0;
if(ans + len < n) p1[cnt1++] = mp(ans, ans + len - 1);
for(int i = t+1; i <= n; i++) {
len = min(len, height[i]);
if(len == 0) return 0;
p1[cnt1++] = mp(sa[i], sa[i] + len - 1);
}
return calc() < kk;
}

void solve(LL now, int n)
{
int t = lower_bound(sum+1, sum+n+1, now) - sum;
int ans = sa[t];
int len = now - sum[t - 1] + height[t];
for(int i = ans; i <= ans + len - 1; i++) printf("%c", s[i]);
printf("\n");
}

void search(int n)
{
LL top = sum
, bot = 1, mid, res;
while(top >= bot) {
mid = (top + bot) >> 1;
if(check(mid, n)) res = mid, top = mid-1;
else bot = mid+1;
}
solve(res, n);
}

void work(void)
{
scanf("%s", s);
int n = strlen(s);
build(n+1, 128);
getheight(n);
for(int i = 1; i <= n; i++) sum[i] = n - sa[i] - height[i];
for(int i = 1; i <= n; i++) sum[i] += sum[i-1];
search(n);
}

int main(void)
{
while(scanf("%d", &kk), kk != 0) work();
return 0;
}