(Relax 后缀数组1.4)POJ 2774 Long Long Message(求两个字符串公共子串的最大长度)

#include <iostream>#include <cstdio>#include <cstring>#include <cmath>#include <algorithm>#include <string>#define Fup(i, s, t) for (int i = s; i <= t; i ++)#define Fdn(i, s, t) for (int i = s; i >= t; i --)#define Path(i, s) for (int i = s; i; i = d[i].next)using namespace std;const int maxn = 200010;struct number {int x;int pos;} num[maxn];struct node {int now;int next;} d[maxn];int val[maxn][2];int c[maxn];int rank[maxn];int sa[maxn];int pos[maxn];int x[maxn];int n;int k;int h[maxn];int height[maxn];string S,s;int sta[maxn], num1[maxn], num2[maxn];bool cmp(const number& a, const number& b) {return a.x < b.x;}void add_value(int u, int v, int i) {d[i].next = c[u];c[u] = i;d[i].now = v;}void radix_sort(int l, int r) {for (int k = 1; k >= 0; --k) {memset(c, 0, sizeof(c));for (int i = r; i >= l; --i) {add_value(val[pos[i]][k], pos[i], i);}int t = 0;for (int i = 0; i <= 200000; ++i) {for (int j = c[i]; j; j = d[j].next) {pos[++t] = d[j].now;}}}int t = 0;for (int i = 1; i <= n; ++i) {if (val[pos[i]][0] != val[pos[i - 1]][0]|| val[pos[i]][1] != val[pos[i - 1]][1]) {t++;}rank[pos[i]] = t;}}bool exist(int len) {int now = 0;int s = 0;for (int i = 1; i <= n; ++i) { //枚举名次数组...if (height[i] < len) {s = max(s, now); //结束当前组now = 1; //now恢复为1} else {now++;}}s = max(s, now);if (s >= k) {return 1;}return 0;}void get_suffix_array() {int t = 1;while (t / 2 <= n) {for (int i = 1; i <= n; ++i) {val[i][0] = rank[i];val[i][1] = (((i + t / 2 <= n) ? rank[i + t / 2] : 0));pos[i] = i;}radix_sort(1, n);t *= 2;}for (int i = 1; i <= n; ++i) {sa[rank[i]] = i;}}void get_common_prefix() {memset(h, 0, sizeof(h));for (int i = 1; i <= n; ++i) {if (rank[i] == 1) {h[i] = 0;} else {int now = 0;if (i > 1 && h[i - 1] > 1) {now = h[i - 1] - 1;}while (now + i <= n && now + sa[rank[i] - 1] <= n&& x[now + i] == x[now + sa[rank[i] - 1]]) {now++;}h[i] = now;}}for (int i = 1; i <= n; ++i) {height[rank[i]] = h[i];}}int binary_search(int l, int r) {while (l <= r) {int mid = (l + r) / 2;if (exist(mid)) {l = mid + 1;} else {r = mid - 1;}}return r;}//***以下是公共子串的最大长度的处理....上面的代码基本是一样的...void init() {cin >> S >> s;n = (int) S.size() + s.size() + 1;string str = S + ' ' + s;Fup(i, 1, n){if (i == (int) S.size() + 1)rank[i] = 27;//这里的27指的是空格作为第27个字符elserank[i] = (int) str[i - 1] - 'a' + 1;x[i] = rank[i];}}void solve() {get_suffix_array();get_common_prefix();int ans = 0;Fup(i, 2, n)if ((sa[i] <= (int) S.size() && sa[i - 1] > (int) S.size() + 1)//只有当suffix(sa[i-1)和suffix(sa[i])不是同一个字符串的两个后缀时,height[i]才是满足条件的..|| (sa[i] > (int) S.size() + 1 && sa[i - 1] <= (int) S.size()))ans = max(ans, height[i]);cout << ans << endl;}int main(){init();solve();return 0;}