[BZOJ1692][Usaco2007 Dec]队列变换

#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cctype>
#include <algorithm>
using namespace std;

int read() {
	int x = 0, f = 1; char c = getchar();
	while(!isdigit(c)){ if(c == ‘-‘) f = -1; c = getchar(); }
	while(isdigit(c)){ x = x * 10 + c - ‘0‘; c = getchar(); }
	return x * f;
}

#define maxn 60010

char S[maxn];
int n, rank[maxn], height[maxn], sa[maxn], Ws[maxn];
bool cmp(int* a, int p1, int p2, int l) {
	if(p1 + l > n && p2 + l > n) return a[p1] == a[p2];
	if(p1 + l > n || p2 + l > n) return 0;
	return a[p1] == a[p2] && a[p1+l] == a[p2+l];
}
void ssort() {
	int *x = rank, *y = height;
	int m = 0;
	for(int i = 1; i <= n; i++) Ws[x[i] = S[i]]++, m = max(m, x[i]);
	for(int i = 1; i <= m; i++) Ws[i] += Ws[i-1];
	for(int i = n; i; i--) sa[Ws[x[i]]--] = i;
	for(int j = 1, pos = 0; pos < n; j <<= 1, m = pos) {
		pos = 0;
		for(int i = n - j + 1; i <= n; i++) y[++pos] = i;
		for(int i = 1; i <= n; i++) if(sa[i] > j) y[++pos] = sa[i] - j;
		for(int i = 1; i <= m; i++) Ws[i] = 0;
		for(int i = 1; i <= n; i++) Ws[x[i]]++;
		for(int i = 1; i <= m; i++) Ws[i] += Ws[i-1];
		for(int i = n; i; i--) sa[Ws[x[y[i]]]--] = y[i];
		swap(x, y); pos = 1; x[sa[1]] = 1;
		for(int i = 2; i <= n; i++) x[sa[i]] = cmp(y, sa[i], sa[i-1], j) ? pos : ++pos;
	}
	return ;
}

int main() {
	n = read();
	for(int i = 1; i <= n; i++) {
		char ch[2]; scanf("%s", ch);
		S[i] = ch[0];
	}
	
	for(int i = n + 1; i <= (n << 1); i++) S[i] = S[(n<<1)-i+1];
	n <<= 1;
//	puts(S + 1);
	ssort();
	for(int i = 1; i <= n; i++) rank[sa[i]] = i;
//	for(int i = 1; i <= n; i++) printf("%d%c", rank[i], i < n ? ‘ ‘ : ‘\n‘);
	
	int l = 1, r = n >> 1;
	for(int i = 1; i <= (n >> 1); i++) {
		if(rank[l] < rank[n-r+1]) putchar(S[l++]);
		else putchar(S[r--]);
		if(i % 80 == 0) putchar(‘\n‘);
	}
	
	return 0;
}