UVA 11107 - Life Forms(尾碼數組)

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UVA 11107 - Life Forms

題目連結

題意：給定一些字串，求最長並且在所有字串的連續子串中出現超過一半次數的字串，輸出這些字串

思路：把這些字串接起來，拼接部分用一個不會出現的不重複的字元，然後求這個長串的尾碼數組，利用height數組去進行二分求解，二分的判斷裡面如果有一個連續height段超過了一半次數，那麼就是可行的，如果所有連續段都沒有出現超過一半，就是不可行的

代碼：

#include <cstdio>#include <cstring>#include <algorithm>#include <set>using namespace std;const int MAXLEN = 200005;struct Suffix {    int s[MAXLEN];    int sa[MAXLEN], t[MAXLEN], t2[MAXLEN], c[MAXLEN], n;    int rank[MAXLEN], height[MAXLEN];    void build_sa(int m) {int i, *x = t, *y = t2;for (i = 0; i < m; i++) c[i] = 0;for (i = 0; i < n; i++) c[x[i] = s[i]]++;for (i = 1; i < m; i++) c[i] += c[i - 1];for (i = n - 1; i >= 0; i--) sa[--c[x[i]]] = i;for (int k = 1; k <= n; k <<= 1) {    int p = 0;    for (i = n - k; i < n; i++) y[p++] = i;    for (i = 0; i < n; i++) if (sa[i] >= k) y[p++] = sa[i] - k;    for (i = 0; i < m; i++) c[i] = 0;    for (i = 0; i < n; i++) c[x[y[i]]]++;    for (i = 0; i < m; i++) c[i] += c[i - 1];    for (i = n - 1; i >= 0; i--) sa[--c[x[y[i]]]] = y[i];    swap(x, y);    p = 1; x[sa[0]] = 0;    for (i = 1; i < n; i++)x[sa[i]] = y[sa[i - 1]] == y[sa[i]] && y[sa[i - 1] + k] == y[sa[i] + k] ? p - 1 : p++;    if (p >= n) break;    m = p;}        }    void getHeight() {int i, j, k = 0;for (i = 0; i < n; i++) rank[sa[i]] = i;for (i = 0; i < n; i++) {    if (k) k--;    if (rank[i] == 0) continue;    int j = sa[rank[i] - 1];    while (s[i + k] == s[j + k]) k++;    height[rank[i]] = k;}    }} gao;const int N = 1005;int n, l, r, id[MAXLEN];char str[N];bool judge(int x, int bo) {    set<int> vis;        vis.insert(id[gao.sa[1]]);    for (int i = 2; i < gao.n; i++) {while (i < gao.n && gao.height[i] >= x) {    vis.insert(id[gao.sa[i]]);    i++;}if (vis.size() * 2 > n) {    if (bo == 0)return true;    for (int j = 0; j < x; j++)printf("%c", gao.s[gao.sa[i - 1] + j]);    printf("\n");}vis.clear();vis.insert(id[gao.sa[i]]);    }    return false;}void solve() {    if (!judge(1, 0)) {printf("?\n");return;    }    l = 1; r++;    while (l < r) {int mid = (l + r) / 2;if (judge(mid, 0)) l = mid + 1;else r = mid;    }    l--;    judge(l, 1);}int main() {    int bo = 0;    while (~scanf("%d", &n) && n) {if (bo) printf("\n");else bo = 1;if (n == 1) {    scanf("%s", str);    printf("%s\n", str);    continue;}int tot = 0;r = 0;for (int i = 0; i < n; i++) {    scanf("%s", str);    int len = strlen(str);    r = max(len, r);    for (int j = 0; j < len; j++) {id[tot] = i;gao.s[tot++] = str[j];    }    id[tot] = i;    gao.s[tot++] = 'z' + i + 1;}gao.n = tot;gao.build_sa('z' + n + 1);gao.getHeight();solve();    }    return 0;}