【POJ3294】Life Forms【后缀数组】【二分】

来源：互联网发布：js后退不刷新页面编辑：程序博客网时间：2024/05/19 20:00

首先二分长度x，将不小于x的height分组。

然后判断连续的一组内，每个后缀所属的每个字符串的个数是否超过一半即可。

二分的时候可以顺便把答案记录下来。

注意每次分组完毕后要给vis清零。

#include <cstdio>#include <cstring>#include <algorithm>using namespace std;const int maxn = 110005, maxd = 105, M = 150;int sa[maxn], rank[maxn], height[maxn];int wa[maxn], wb[maxn], wv[maxn], cnt[maxn];void SA(int *r, int n, int m) {int *x = wa, *y = wb;for(int i = 0; i < m; i++) cnt[i] = 0;for(int i = 0; i < n; i++) cnt[x[i] = r[i]]++;for(int i = 1; i < m; i++) cnt[i] += cnt[i - 1];for(int i = n - 1; i >= 0; i--) sa[--cnt[x[i]]] = i;for(int j = 1; j < n; j <<= 1) {int p = 0;for(int i = n - j; i < n; i++) y[p++] = i;for(int i = 0; i < n; i++) if(sa[i] >= j) y[p++] = sa[i] - j;for(int i = 0; i < n; i++) wv[i] = x[y[i]];for(int i = 0; i < m; i++) cnt[i] = 0;for(int i = 0; i < n; i++) cnt[wv[i]]++;for(int i = 1; i < m; i++) cnt[i] += cnt[i - 1];for(int i = n - 1; i >= 0; i--) sa[--cnt[wv[i]]] = y[i];swap(x, y);p = 1; x[sa[0]] = 0;for(int i = 1; i < n; i++)x[sa[i]] = y[sa[i - 1]] == y[sa[i]] && y[sa[i - 1] + j] == y[sa[i] + j] ? p - 1 : p++;if(p >= n) break;m = p;}}void calcHeight(int *r, int n) {int i, j, k;for(i = j = k = 0; i < n; height[rank[i++]] = k)for(k ? k-- : 0, j = sa[rank[i] - 1]; r[i + k] == r[j + k]; k++);}int n, s[maxn], pos[maxd], ans[maxn];char str[maxn];bool vis[maxd];bool check(int x, int len, int k) {for(int i = 0; i < maxd; i++) vis[i] = 0;int size = 0, tot = 0;for(int i = 1; i <= len; i++) {if(height[i] >= x) {for(int j = 1; j <= n; j++) {if(pos[j - 1] < sa[i] && sa[i] < pos[j]) tot += !vis[j], vis[j] = 1;if(pos[j - 1] < sa[i - 1] && sa[i - 1] < pos[j]) tot += !vis[j], vis[j] = 1;}} else {if(tot > k) ans[++size] = sa[i - 1];tot = 0;for(int j = 0; j < maxd; j++) vis[j] = 0;}}if(tot > k) ans[++size] = sa[len];if(size) return ans[0] = size;return 0;} int main() {while(1) {scanf("%d", &n);if(n == 0) break;int len = 0, end = 0;for(int i = 0; i < n; i++) {scanf("%s", str + len);for(; str[len] != '\0'; len++) s[len] = str[len] - 'a' + 100;s[len] = ++end;pos[i + 1] = len++;}s[--len] = 0;SA(s, len + 1, M);for(int i = 0; i <= len; i++) rank[sa[i]] = i;calcHeight(s, len);int l = 1, r = len + 1, k = n >> 1;while(l <= r) {int mid = l + r >> 1;if(check(mid, len + 1, k)) l = mid + 1;else r = mid - 1;}if(l == 1) printf("?\n");elsefor(int i = 1; i <= ans[0]; i++) {for(int j = ans[i]; j < ans[i] + l - 1; j++)printf("%c", str[j]);printf("\n");}printf("\n");}return 0;}

0 0