【URAL 1297】Palindrome 最长回文子串

模板题,,,模板打错查了1h+QAQ

#include<cmath>
#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;
const int N = 1000003;

int t1[N], t2[N], c[N], f[N][30];
void st(int *x, int *y, int *sa, int n, int m) {
	int i;
	for(i = 0; i < m; ++i) c[i] = 0;
	for(i = 0; i < n; ++i) ++c[x[y[i]]];
	for(i = 1; i < m; ++i) c[i] += c[i - 1];
	for(i = n - 1; i >= 0; --i) sa[--c[x[y[i]]]] = y[i];
}
void mkhz(int *a, int *sa, int n, int m) {
	int *t, *x = t1, *y = t2, i, j, p;
	for(i = 0; i < n; ++i) x[i] = a[i], y[i] = i;
	st(x, y, sa, n, m);
	for(j = 1, p = 1; p < n; j <<= 1, m = p) {
		for(p = 0, i = n - j; i < n; ++i) y[p++] = i;
		for(i = 0; i < n; ++i) if (sa[i] >= j) y[p++] = sa[i] - j;
		st(x, y, sa, n, m);
//		for(i = 1; i < n; ++i) printf("%d ", sa[i]); puts("");
		for(t = x, x = y, y = t, p = 1, x[sa[0]] = 0, p = 1, i = 1; i < n; ++i)
			x[sa[i]] = y[sa[i]] == y[sa[i - 1]] && y[sa[i] + j] == y[sa[i - 1] + j] ? p - 1 : p++;
		}
}
void mkh(int *r, int *sa, int *rank, int *h, int n) {
	int k = 0, i, j;
	for(i = 1; i <= n; ++i) rank[sa[i]] = i;
	for(i = 1; i <= n; h[rank[i++]] = k)
		for(k ? k-- : 0, j = sa[rank[i] - 1]; r[i + k] == r[j + k]; ++k);
}
void mkst(int *h, int n) {
	int k = floor(log((double)n) / log(2.0));
	for(int i = 1; i <= n; ++i)
		f[i][0] = h[i];
	for(int j = 1; j <= k; ++j)
		for(int i = 1; i <= n; ++i) {
			if (i + (1 << j) - 1 > n) break;
			f[i][j] = min(f[i][j - 1], f[i + (1 << (j - 1))][j - 1]);
		}
}

char s[N];
int n, sa[N], a[N], rank[N], h[N];
int rmq(int l, int r) {
	l = rank[l]; r = rank[r];
	if (l > r) swap(l, r); ++l;
	int k = floor(log((double)(r - l + 1)) / log(2.0));
	return min(f[l][k], f[r - (1 << k) + 1][k]);
}
int main() {
	while (scanf("%s", s + 1) != EOF) {
		n = strlen(s + 1);
		for(int i = 1; i <= n; ++i) a[i] = s[i];
		a[n + 1] = 126;
		for(int i = 1; i <= n; ++i)
			a[n + 1 + i] = a[n + 1 - i];
		mkhz(a, sa, n * 2 + 2, 130);
		mkh(a, sa, rank, h, n * 2 + 1);
		mkst(h, n * 2 + 1);
//		for(int i = 1; i <= n * 2 + 1; ++i) printf("%d ", sa[i]); puts("");
//		for(int i = 1; i <= n * 2 + 1; ++i) printf("%d ", rank[i]); puts("");
		int ans = 0, x, h, t;
		for(int i = 1; i <= n; ++i) {
//			ans = max(ans, rmq(i, 2 * n + 2 - i) * 2 - 1);
//			if (i != 1 && a[i - 1] == a[i]) ans = max(ans, rmq(i, 2 * n + 3 - i) * 2);
			if ((x = rmq(i, 2 * n + 2 - i)) * 2 - 1 > ans)
				ans = x * 2 - 1, h = i - x + 1, t = i + x - 1;
			if (i != 1 && a[i - 1] == a[i] && (x = rmq(i, 2 * n + 3 - i)) * 2 > ans)
				ans = x * 2, h = i - x , t = i + x - 1;
//			printf("%d\n", ans);
		}
		for(int i = h; i <= t; ++i)
			putchar(s[i]);
		puts("");
//		printf("%d\n", ans);
	}
	return 0;
}

第一次把调试信息放在代码里,会不会显得我很制杖呢?(水题都调了这么多)

posted @ 2016-04-21 14:26  abclzr  阅读(197)  评论(0编辑  收藏  举报