diff --git a/include/s0028_find_the_index_of_the_first_occurrence_in_a_string.hpp b/include/s0028_find_the_index_of_the_first_occurrence_in_a_string.hpp
new file mode 100644
index 0000000..5c3211b
--- /dev/null
+++ b/include/s0028_find_the_index_of_the_first_occurrence_in_a_string.hpp
@@ -0,0 +1,13 @@
+#ifndef S0028_FIND_THE_INDEX_OF_THE_FIRST_OCCURRENCE_IN_A_STRING
+#define S0028_FIND_THE_INDEX_OF_THE_FIRST_OCCURRENCE_IN_A_STRING
+
+#include <string>
+
+using namespace std;
+
+class Solution {
+ public:
+  int strStr(string haystack, string needle);
+};
+
+#endif
diff --git a/src/s0028_find_the_index_of_the_first_occurrence_in_a_string.cpp b/src/s0028_find_the_index_of_the_first_occurrence_in_a_string.cpp
new file mode 100644
index 0000000..0617f6d
--- /dev/null
+++ b/src/s0028_find_the_index_of_the_first_occurrence_in_a_string.cpp
@@ -0,0 +1,18 @@
+#include "s0028_find_the_index_of_the_first_occurrence_in_a_string.hpp"
+
+int Solution::strStr(string haystack, string needle) {
+  int haystackLen = haystack.length();
+  int needleLen = needle.length();
+  for (int i{0}; i < haystackLen; ++i) {
+    for (int j{0}, iTmp = i; j < needleLen; ++j) {
+      if (haystack[iTmp] != needle[j]) {
+        break;
+      } else if (j == needleLen - 1) {
+        return i;
+      } else {
+        ++iTmp;
+      }
+    }
+  }
+  return -1;
+}
diff --git a/tests/s0028_find_the_index_of_the_first_occurrence_in_a_string.cpp b/tests/s0028_find_the_index_of_the_first_occurrence_in_a_string.cpp
new file mode 100644
index 0000000..6c83072
--- /dev/null
+++ b/tests/s0028_find_the_index_of_the_first_occurrence_in_a_string.cpp
@@ -0,0 +1,19 @@
+#include "s0028_find_the_index_of_the_first_occurrence_in_a_string.hpp"
+
+#include <gtest/gtest.h>
+
+TEST(Problem28, Case1) {
+  string haystack{"sadbutsad"};
+  string needle{"sad"};
+  int o{0};
+  Solution solution;
+  EXPECT_EQ(solution.strStr(haystack, needle), o);
+}
+
+TEST(Problem28, Case2) {
+  string haystack{"leetcode"};
+  string needle{"leeto"};
+  int o{-1};
+  Solution solution;
+  EXPECT_EQ(solution.strStr(haystack, needle), o);
+}