Submission #486534

#	Time	Username	Problem	Language	Result	Execution time	Memory
486534		rainboy	Palinilap (COI16_palinilap)	C11	54 / 100	1090 ms	24056 KiB

palinilap

#include <stdio.h>
#include <string.h>

#define N	100100
#define A	26

long long max(long long a, long long b) { return a > b ? a : b; }

void manacher(char *cc, int *rr, int n) {
	static char cc_[N * 2 + 1];
	static int rr_[N * 2];
	int i, o, x;

	for (i = 0; i < n * 2 + 1; i++)
		cc_[i] = i % 2 == 1 ? cc[i / 2] : ' ';
	for (i = 0, o = 0, x = 0; i < n * 2 + 1; i++)
		if (i + rr_[o + o - i] < x)
			rr_[i] = rr_[o + o - i];
		else {
			o = i, x = max(x, i);
			while (x >= 0 && x < n * 2 + 1 && cc_[x] == cc_[o + o - x])
				x++;
			rr_[i] = x - o;
		}
	for (i = 0; i <= n - 1 + n - 1; i++)
		rr[i] = rr_[i + 1] / 2;
}

int main() {
	static long long kk[N][A], ll[N], mm[N];
	static int rr[N * 2];
	static char cc[N + 1];
	int n, h, i, i_, j, j_, ij, a;
	long long k_;

	scanf("%s", cc), n = strlen(cc);
	manacher(cc, rr, n);
	for (ij = 0; ij <= n - 1 + n - 1; ij++) {
		h = ij / 2, i_ = h - rr[ij], j_ = ij - i_;
		if (ij % 2 == 0) {
			ll[h] += h - i_, ll[h + 1] -= (h - i_) * 2, ll[h + 2] += h - i_;
			mm[h] -= h - i_, mm[h + 1] += (h - i_) * 2, mm[h + 2] -= h - i_;
		}
		ll[0] += h - i_, ll[1] -= h - i_;
		ll[i_ + 1]--, ll[h + 1]++, ll[ij - h + 1]++, ll[j_ + 1]--;
		mm[i_ + 1]++, mm[h + 1]--, mm[ij - h + 1]--, mm[j_ + 1]++;
		for (i = i_, j = j_; i >= 0 && j < n; i--, j++) {
			if (i < i_ && cc[i] != cc[j])
				break;
			kk[i_][cc[j_] - 'a']++, kk[j_][cc[i_] - 'a']++;
		}
	}
	for (i = 1; i < n; i++)
		ll[i] += ll[i - 1];
	for (i = 1; i < n; i++)
		ll[i] += ll[i - 1];
	for (i = 1; i < n; i++)
		mm[i] += mm[i - 1];
	for (i = 1; i < n; i++)
		mm[i] += mm[i - 1];
	k_ = 0;
	for (i = 0; i < n; i++)
		for (a = 0; a < A; a++)
			k_ = max(k_, kk[i][a] + ll[i] + (cc[i] == a + 'a' ? mm[i] : 0));
	printf("%lld\n", k_);
	return 0;
}

Compilation message (stderr)

palinilap.c: In function 'main':
palinilap.c:36:2: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
   36 |  scanf("%s", cc), n = strlen(cc);
      |  ^~~~~~~~~~~~~~~

• Subtask 1: 17 / 17
• Subtask 2: 37 / 37
• Subtask 3: 0 / 46