Update suffix_array.cpp

Changes

1 changed files (+18/-3)

• String/suffix_array.cpp
  • @@ -3,7 +3,7 @@
    #include <string> using namespace std; - vector<int> suffix_array(string &S) { + vector<int> suffix_array(string& S) { int N = S.length(); vector<int> SA(N), rank(N); for (int i = 0; i < N; i++) {
  • @@ -14,10 +14,9 @@ vector<int> suffix_array(string &S) {
    for (int t = 1; t < N; t <<= 1) { vector<int> tmp(rank); for (int i = 0; i < N; i++) { - bool s = i && SA[i - 1] + t < N && tmp[SA[i]] == tmp[SA[i - 1]] && tmp[SA[i] + t >> 1] == tmp[SA[i - 1] + t >> 1]; + bool s = i && SA[i - 1] + t < N && tmp[SA[i]] == tmp[SA[i - 1]] && tmp[SA[i] + (t >> 1)] == tmp[SA[i - 1] + (t >> 1)]; rank[SA[i]] = s ? rank[SA[i - 1]] : i; } - tmp = SA; vector<int> cnt(N); for (int i = 0; i < N; i++) cnt[i] = i;
  • @@ -28,3 +27,19 @@ vector<int> suffix_array(string &S) {
    } return SA; } + + vector<int> lcp_array(const vector<int>& SA, string& S) { + int N = S.size(); + vector<int> rank(N), LCP(N - 1); + for (int i = 0; i < N; i++) rank[SA[i]] = i; + int pre = 0; + for (int i = 0; i < N; i++) { + if (rank[i] < N - 1) { + int j = SA[rank[i] + 1]; + while (max(i, j) + pre < S.size() && S[i + pre] == S[j + pre]) pre++; + LCP[rank[i]] = pre; + if (pre > 0) pre--; + } + } + return LCP; + }