Add problem4 implementation and update CMakeLists and main.cpp

CMakeLists.txt

@@ -9,4 +9,6 @@ add_executable(data_structure_homework main.cpp
         problem2.cpp
         problem2.h
         problem3.cpp
-        problem3.h)
+        problem3.h
+        problem4.cpp
+        problem4.h)

main.cpp

@@ -4,6 +4,7 @@
 #include "problem1.h"
 #include "problem2.h"
 #include "problem3.h"
+#include "problem4.h"
 
 int main() {
     problem_1();
@@ -11,4 +12,6 @@ int main() {
     problem_2();
     std::cout << "------------------------" << std::endl;
     problem_3();
+    std::cout << "------------------------" << std::endl;
+    problem_4();
 }

problem4.cpp

@@ -0,0 +1,41 @@
+//
+// Created by grtsinry43 on 5/8/25.
+//
+
+#include "problem4.h"
+
+#include <iostream>
+#include <string>
+#include <vector>
+
+std::vector<int> naive_string_match(const std::string &text, const std::string &pattern) {
+    std::vector<int> positions;
+    int text_length = text.size();
+    int pattern_length = pattern.size();
+
+    for (int i = 0; i <= text_length - pattern_length; ++i) {
+        int j = 0;
+        while (j < pattern_length && text[i + j] == pattern[j]) {
+            ++j;
+        }
+        if (j == pattern_length) {
+            positions.push_back(i); // 记录匹配的起始位置
+        }
+    }
+    return positions;
+}
+
+int problem_4() {
+    std::string text = "ababcabcacbab";
+    std::string pattern = "abc";
+
+    std::vector<int> positions = naive_string_match(text, pattern);
+
+    std::cout << "Pattern found at positions: ";
+    for (int pos : positions) {
+        std::cout << pos << " ";
+    }
+    std::cout << std::endl;
+
+    return 0;
+}

problem4.h

@@ -0,0 +1,10 @@
+//
+// Created by grtsinry43 on 5/8/25.
+//
+
+#ifndef PROBLEM4_H
+#define PROBLEM4_H
+
+int problem_4();
+
+#endif //PROBLEM4_H