added problem 16

sayampradhan · sayampradhan · commit e9c7563d6b2a · 2026-03-31T15:48:31.000+05:30
diff --git a/CMakeLists.txt b/CMakeLists.txt
@@ -55,4 +55,5 @@ add_executable(cpp_evolution
         phase-3-data-structures/10_buy-sell.cpp
         phase-3-data-structures/11_anagrams.cpp
         phase-3-data-structures/12_reverse_string.cpp
-        phase-3-data-structures/15_remove_spaces.cpp)
+        phase-3-data-structures/15_remove_spaces.cpp
+        phase-3-data-structures/16_check_substrings_manually.cpp)
diff --git a/phase-3-data-structures/16_check_substrings_manually.cpp b/phase-3-data-structures/16_check_substrings_manually.cpp
@@ -0,0 +1,44 @@
+// credits: https://www.geeksforgeeks.org/dsa/check-string-substring-another/
+// C++ program to check if a string is substring of other
+// using nested loops
+
+#include <iostream>
+using namespace std;
+
+// Function to find if pat is a substring of txt
+int findSubstring(string &txt, string &pat) {
+    int n = txt.length();
+    int m = pat.length();
+
+    // Iterate through txt
+    for (int i = 0; i <= n - m; i++) {
+
+        // Check for substring match
+        int j;
+        for (j = 0; j < m; j++) {
+
+            // Mismatch found
+            if (txt[i + j] != pat[j]) {
+                break;
+            }
+        }
+
+        // If we completed the inner loop, we found a match
+        if (j == m) {
+
+            // Return starting index
+            return i;
+        }
+    }
+
+    // No match found
+    return -1;
+}
+
+int main() {
+    string txt = "sayamapradhan";
+    string pat = "a";
+    cout << findSubstring(txt, pat);
+
+    return 0;
+}
