str/kmp.hpp

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Last update: 2024-11-09 00:49:07+00:00
Include: #include "str/kmp.hpp"

Depends on

prelude.hpp

Verified with

test/str/kmp.test.cpp

Code

#pragma once
#include "prelude.hpp"

// pi[i] = max { k : s[0..k) == s[i-k..i) }
template <class It>
vector<int> kmp(It s, It s_last) {
  int n = s_last - s;
  vector<int> pi(n + 1);
  pi[0] = -1;
  int len = 0;
  rep2(i, 1, n) {
    while (len != -1 && s[len] != s[i])
      len = pi[len];
    pi[i + 1] = ++len;
  }
  return pi;
}

template <class It1, class It2>
vector<int> occurences(It1 s, It1 s_last, It2 p, It2 p_last) {
  int n = s_last - s, m = p_last - p;
  auto pi = kmp(p, p_last);
  vector<int> res;
  res.reserve(max(0, n - m + 1));
  int i = 0, len = 0;
  while (i < n - m + 1) {
    while (len < m && s[i + len] == p[len]) len++;
    if (len == m) res.push_back(i);
    i += len - pi[len];
    len = pi[len] == -1 ? 0 : pi[len];
  }
  return res;
}

#line 2 "prelude.hpp"
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using vi = vector<int>;
using vvi = vector<vector<int>>;
using vll = vector<ll>;
using vvll = vector<vector<ll>>;
using vc = vector<char>;
#define rep2(i, m, n) for (auto i = (m); i < (n); i++)
#define rep(i, n) rep2(i, 0, n)
#define repr2(i, m, n) for (auto i = (n); i-- > (m);)
#define repr(i, n) repr2(i, 0, n)
#define all(x) begin(x), end(x)
auto ndvec(int n, auto e) { return vector(n, e); }
auto ndvec(int n, auto ...e) { return vector(n, ndvec(e...)); }
auto comp_key(auto&& f) { return [&](auto&& a, auto&& b) { return f(a) < f(b); }; }
auto& max(const auto& a, const auto& b) { return a < b ? b : a; }
auto& min(const auto& a, const auto& b) { return b < a ? b : a; }
#if __cpp_lib_ranges
namespace R = std::ranges;
namespace V = std::views;
#endif
#line 3 "str/kmp.hpp"

// pi[i] = max { k : s[0..k) == s[i-k..i) }
template <class It>
vector<int> kmp(It s, It s_last) {
  int n = s_last - s;
  vector<int> pi(n + 1);
  pi[0] = -1;
  int len = 0;
  rep2(i, 1, n) {
    while (len != -1 && s[len] != s[i])
      len = pi[len];
    pi[i + 1] = ++len;
  }
  return pi;
}

template <class It1, class It2>
vector<int> occurences(It1 s, It1 s_last, It2 p, It2 p_last) {
  int n = s_last - s, m = p_last - p;
  auto pi = kmp(p, p_last);
  vector<int> res;
  res.reserve(max(0, n - m + 1));
  int i = 0, len = 0;
  while (i < n - m + 1) {
    while (len < m && s[i + len] == p[len]) len++;
    if (len == m) res.push_back(i);
    i += len - pi[len];
    len = pi[len] == -1 ? 0 : pi[len];
  }
  return res;
}