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#28 Implement strStr.cpp
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#28 Implement strStr.cpp
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#include <string>
#include <algorithm>
#include <map>
#include <vector>
#include <deque>
//Implement strStr()
//https://leetcode.com/problems/implement-strstr/
class Solution {
public:
int RabinKarp(const std::string& text, const std::string& pattern) {
int d = 10;
if (pattern.size() == 0) {
return 0;
}
else if (text.size() < pattern.size()) {
return -1;
}
size_t j;
int pattern_hash = 0;
int text_hash = 0;
int h = 1;
for (size_t i = 0; i < pattern.size() - 1; i++) {
h = (h * d) % (d + 3);
}
for (size_t i = 0; i < pattern.size(); i++) {
pattern_hash = (d * pattern_hash + pattern[i]) % (d + 3);
text_hash = (d * text_hash + text[i]) % (d + 3);
}
// Знаходимо співпадіння
for (size_t i = 0; i <= text.size() - pattern.size(); i++) {
if (pattern_hash == text_hash) {
for (j = 0; j < pattern.size(); j++) {
if (text[i + j] != pattern[j]) {
break;
}
}
if (j == pattern.size()) {
return i;
}
}
if (i < text.size() - pattern.size()) {
text_hash = (d * (text_hash - text[i] * h) + text[i + pattern.size()]) % (d + 3);
if (text_hash < 0) {
text_hash = (text_hash + (d + 3));
}
}
}
return -1;
}
int naive(const std::string& text, const std::string& pattern)
{
if (pattern.size() == 0) {
return 0;
}
else if (text.size() < pattern.size()) {
return -1;
}
for (size_t i = 0; i <= text.size() - pattern.size(); i++) {
size_t j;
for (j = 0; j < pattern.size(); j++) {
if (text[i + j] != pattern[j]) {
break;
}
}
if (j == pattern.size()) {
return i;
}
}
return -1;
}
bool HORSPOOL_check_loop(const std::string& text, const std::string& pattern, size_t& checked_end, size_t& pos,
const std::map<char, size_t>& last) {
for (;; pos--) {
char checked = text[checked_end - (pattern.size() - 1) + pos];
if (pattern[pos] != checked) {
try {
pos = last.at(text[checked_end]);
checked_end += pattern.size() - 1 - pos;
pos = pattern.size() - 1;
}
catch (const std::exception&) {
pos = pattern.size() - 1;
checked_end += pattern.size();
}
return false;
}
if (pos == 0) {
return true;
}
}
}
int HORSPOOL(const std::string& text, const std::string& pattern)
{
if (pattern.size() == 0) {
return 0;
}
else if (text.size() < pattern.size()) {
return -1;
}
std::map<char, size_t>last;
for (size_t i = 0; i < pattern.size() - 1; i++) {
last[pattern[i]] = i;
}
size_t checked_end = pattern.size() - 1;
size_t pos = checked_end;
while (checked_end < text.size()) {
if (HORSPOOL_check_loop(text, pattern, checked_end, pos, last)) {
return checked_end + 1 - pattern.size();
}
}
return -1;
}
};