pointers; fix heap corruption

pr4.cpp

@@ -16,15 +16,15 @@ public:
         capacity = Capacity;
         p = new char[capacity];
         len = 0;
+        p[0] = '\0'; // Initialize with an empty string
     }
 
     explicit BaseString(const char* ptr) //create object from input string
-    // mark Single-argument constructors explicit to avoid unintentional implicit conversions
+        // mark Single-argument constructors explicit to avoid unintentional implicit conversions
     {
         cout << "\nBase Constructor 1\n";
         len = Length(ptr);
-        capacity = len; // allocate needed memory dynamically based on the Length of the input.
-        //avoid unnecessary memory allocation.
+        capacity = len + 1; // allocate needed memory dynamically based on the Length of the input including null terminator
         p = new char[capacity];
         CopyString(p, ptr, len);
     }
@@ -53,7 +53,7 @@ public:
         {
             *destination++ = *source++;
         }
-        *destination = '\0';
+        *destination = '\0'; // Ensure the destination is null-terminated
     }
 
     int Length() const { return len; }
@@ -76,20 +76,22 @@ public:
     }
 
     BaseString(const BaseString& s) // copy constructor
-    // using const can avoid  unnecessary copying of objects
+        // using const can avoid unnecessary copying of objects
     {
         cout << "\nBase Copy Constructor\n";
         len = s.Length();
-        p = new char[s.capacity];
         capacity = s.capacity;
+        p = new char[capacity];
         CopyString(p, s.p, len);
     }
 
     virtual void print() const
     {
-        for (int i = 0; i < len; i++)
+        const char* ptr = p;
+        while (*ptr != '\0')
         {
-            cout << p[i];
+            cout << *ptr;
+            ptr++;
         }
     }
 
@@ -118,7 +120,7 @@ public:
         return *this;
     }
 
-    DerivedString(const DerivedString& s) : BaseString(s) // using const can avoid  unnecessary copying of objects
+    DerivedString(const DerivedString& s) : BaseString(s) // using const can avoid unnecessary copying of objects
     {
         cout << "\nDerived Copy Constructor\n";
     }
@@ -132,24 +134,26 @@ public:
     int LastIndexOf(const char* substr) const
     {
         int substrLen = BaseString::Length(substr);
-        int startPos = len; // Start searching from the end of the string
-        while (startPos >= 0)
+        if (substrLen > len) return -1; // substr longer than the string
+
+        const char* start = p + len - substrLen; // Start from the last possible position
+        while (start >= p)
         {
-            int i = 0;
-            while (i < substrLen && p[startPos + i] == substr[i])
+            const char* current = start;
+            const char* sub = substr;
+            while (*sub != '\0' && *current == *sub)
             {
-                i++;
+                current++;
+                sub++;
             }
-            if (i == substrLen) // If the entire substring matches
+            if (*sub == '\0') // If the entire substring matches
             {
-                return startPos;
+                return start - p;
             }
-            startPos--; // Move to the previous position
+            start--;
         }
         return -1; // Not found
     }
-
-
 };
 
 int main() {