Submission #7608

#	Time	Username	Problem	Language	Result	Execution time	Memory
7608		hongjun7	Palindromes (APIO14_palindrome)	C++98	0 / 100	0 ms	61732 KiB

palindrome

#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <algorithm>
using namespace std;
#define MK 21
#define MN 300005
int n, cnt, ord[MK][MN], lcp[MK][MN], K, sc[MN], dyn[MN<<1];
char _S[MN], S[MN*2];
long long res;
struct data {
	int a, b, x;
	bool operator < (const data p) const {
		if (a == p.a) return b < p.b;
		return a < p.a;
	}
} w[MN], v[MN];
void upd(int a, int b) {
	int L = b-a+1, t = ord[K][a], lo = t, hi = t;
	for (int i = K; i >= 0; i--) {
		if (lo >= (1<<i) && lcp[i][lo-(1<<i)] >= L) lo -= (1<<i);
		if (lcp[i][hi] >= L) hi += (1<<i);
	}
	res = max(res, (long long)(hi-lo+1)*L);
}
int main() {
	int i, j;
	scanf("%s",_S);
	n = strlen(_S);
	int k = 1, M = 'z';
	for (i = 0; i < n; i++) v[i].a = _S[i], v[i].b = 0, v[i].x = i;
	while (1) {
		for (i = 0; i <= n-1; i++) sc[v[i].a]++;
		for (i = 1; i <= M; i++) sc[i] += sc[i-1];
		for (i = n-1; i >= 0; i--) w[--sc[v[i].a]] = v[i];
		for (i = 1; i <= M; i++) sc[i] = 0;
		cnt = 0;
		for (i = 0; i < n; i++) {
			if (!i || w[i].a != w[i-1].a || w[i].b != w[i-1].b) cnt++;
			ord[K][w[i].x] = cnt;
		}
		if (k >= n) break;
		M = cnt; cnt = n-1;
		for (i = n-1; i >= 0; i--) {
			if (w[i].x < k) continue;
			v[cnt].a = ord[K][w[i].x-k], v[cnt].b = ord[K][w[i].x], v[cnt--].x = w[i].x-k;
		}
		for (i = n-k; i < n; i++) v[cnt].a = ord[K][i], v[cnt].b = 0, v[cnt--].x = i;
		k<<=1;
		K++;
	}
	for (i = 1; i < n; i++) {
		int w1 = w[i-1].x, w2 = w[i].x;
		for (j = K; j >= 0; j--) if (ord[j][w1] == ord[j][w2]) w1 += (1<<j), w2 += (1<<j), lcp[0][i] += (1<<j);
	}
	for (i = 0; i < K; i++) for (j = 1; j < n-(1<<i); j++) lcp[i+1][j] = min(lcp[i][j], lcp[i][j+(1<<i)]);
	for (i = 0; _S[i]; i++) S[i*2] = _S[i], S[i*2+1] = '-';
	int m = n*2-1;
	M = 0;
	for (i = 0; i < m; i++) {
		if (i < M && dyn[j*2-i] < M-i-1) { dyn[i] = dyn[j*2-i]; continue; }
		j = i;
		while (M < m && M <= i*2 && S[M] == S[i*2-M]) {
			M++;
			if (!(M&1)) continue;
			upd((i*2-M-1)/2, (M-1)/2);
		}
		dyn[i] = M-i-1;
	}
	printf("%lld", res);
}

• Subtask 1: 0 / 8
• Subtask 2: 0 / 15
• Subtask 3: 0 / 24
• Subtask 4: 0 / 26
• Subtask 5: 0 / 27