restructure + add boyer moore algo

Author: stoychoX

algorithms/strings/boyer-moore.cpp

@@ -0,0 +1,104 @@
+#include<iostream>
+#include<vector>
+#include<limits>
+#include<algorithm>
+#include<fstream>
+
+#define APLHABET_SIZE CHAR_MAX
+
+struct pattern {
+	std::string pat;
+
+	std::vector<size_t> badChar;
+	std::vector<size_t> goodSuffix;
+};
+
+void initGoodSuffix(const std::string& str, std::vector<size_t>& arg) {
+	arg.resize(str.size() + 1, 0);
+	std::vector<size_t> bpos(str.size() + 1, 0);
+
+	int currentChar = str.length();
+
+	int beg = str.length() + 1;
+
+	bpos[currentChar] = beg;
+
+	while(currentChar > 0) {
+		while(beg <= str.length() && str[currentChar - 1] != str[beg - 1]) {
+			if(arg[beg] == 0)
+				arg[beg] = beg - currentChar;
+
+			beg = bpos[beg];
+		}
+
+		currentChar--;
+		beg--;
+		bpos[currentChar] = beg;
+	}
+
+	int j = bpos[0];
+
+	for (size_t i = 0; i < str.size(); i++) {
+		if(arg[i] == 0)
+			arg[i] = j;
+		
+		if(i == j)
+			j = bpos[j];
+	}
+}
+
+void initBadChar(const std::string& str, std::vector<size_t>& arg) {
+	arg.resize(APLHABET_SIZE, str.length());
+
+	for (size_t i = 0; i < str.length(); i++)
+		arg[str[i]] = str.length() - i - 1;
+}
+
+void initPattern(const std::string& str, pattern& arg) {
+	arg.pat = str;
+	initBadChar(str, arg.badChar);
+	initGoodSuffix(str, arg.goodSuffix);
+}
+
+void printTables(const pattern& arg) {
+	std::cout << "Bad char: " << std::endl; 
+	for(auto x : arg.badChar)
+		std::cout << x << " ";
+
+	std::cout << std::endl;
+	std::cout << "Good suffix: " << std::endl; 
+
+	for(auto x : arg.goodSuffix)
+		std::cout << x << " ";
+	std::cout << std::endl;
+}
+
+void search(const std::string& str, const pattern& arg) {
+	int indexPosition = arg.pat.size() - 1;
+
+	while(indexPosition < str.length()) {
+		int indexString = indexPosition;
+		int indexPattern = arg.pat.size() - 1;
+
+		while(indexPattern >= 0 && str[indexString] == arg.pat[indexPattern]) {
+			--indexPattern;
+			--indexString;
+		}
+
+		if(indexPattern < 0) {
+            // cout in search just for the demo.
+			std::cout << "Matched at " << indexPosition - arg.pat.length() + 1 << std::endl;
+			indexPosition += arg.goodSuffix[0];
+		}
+		else {
+			indexPosition += std::max(arg.badChar[str[indexString]], arg.goodSuffix[indexPattern + 1]);
+		}
+	}
+}
+
+int main() {
+	std::string text = "This is some text where we search given pattern. Write pattern second time.";
+    pattern p;
+    initPattern("pattern",p);
+    search(text, p);
+}