【后缀数组】 HDOJ 5030 Rabbit's String

先二分答案。。。然后用后缀数组判断一下目前答案在分成k部分的时候是否成立。。。

#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[n], 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;
}


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