whenever you allocate memory on the heap using the new keyword you th…

…en have to free that memory using delete

Data-Structures/Trees/problems/check-for-balanced-bt.cpp

@@ -39,6 +39,14 @@ class Solution {
 
         return max(lh, rh) + 1;
     }
+
+    void deleteTree(TreeNode* node) {
+        if (node != NULL) {
+            deleteTree(node->left);
+            deleteTree(node->right);
+            delete node;
+        }
+    }
 };
 
 int main() {
@@ -54,5 +62,7 @@ int main() {
 
     bool isBalancedResult = solution.isBalanced(balancedTree);
     cout << "tree balanced? " << (isBalancedResult ? "Yes" : "No") << endl;
+
+    solution.deleteTree(balancedTree);
     return 0;
 }

Data-Structures/Trees/problems/count-leaves.cpp

@@ -22,6 +22,13 @@ class Solution {
 
         return leftLeaves + rightLeaves;
     }
+    void deleteTree(TreeNode* node) {
+        if (node != NULL) {
+            deleteTree(node->left);
+            deleteTree(node->right);
+            delete node;
+        }
+    }
 };
 
 int main() {
@@ -37,5 +44,6 @@ int main() {
     int result = solution.countLeaves(root);
     cout << "Sum of left leaves: " << result << std::endl;
 
+    solution.deleteTree(root);
     return 0;
 }

Data-Structures/Trees/problems/depth-of-bt.cpp

@@ -34,6 +34,13 @@ class Solution {
         int rh = minDepth(root->right);
         return 1 + min(lh, rh); // formula
     }
+    void deleteTree(TreeNode* node) {
+        if (node != NULL) {
+            deleteTree(node->left);
+            deleteTree(node->right);
+            delete node;
+        }
+    }
 };
 
 int main() {
@@ -50,5 +57,6 @@ int main() {
     std::cout << "Max Depth of tree : " << maxDepth << std::endl;
     std::cout << "Min Depth of tree : " << minDepth << std::endl;
 
+    solution.deleteTree(root);
     return 0;
 }

Data-Structures/Trees/problems/sum-of-left-leaves.cpp

@@ -27,6 +27,13 @@ class Solution {
 
         return sum;
     }
+    void deleteTree(TreeNode* node) {
+        if (node != NULL) {
+            deleteTree(node->left);
+            deleteTree(node->right);
+            delete node;
+        }
+    }
 };
 
 int main() {
@@ -41,5 +48,6 @@ int main() {
     int result = solution.sumOfLeftLeaves(root);
     std::cout << "Sum of left leaves: " << result << std::endl;
 
+    solution.deleteTree(root);
     return 0;
 }

Data-Structures/Trees/problems/symmetric-bt.cpp

@@ -26,6 +26,15 @@ class Solution {
         return helper(left->left, right->right) &&
                helper(left->right, right->left);
     }
+    // recursively free the memory of all the nodes
+    // call this function at the end of the program
+    void deleteTree(TreeNode* node) {
+        if (node != NULL) {
+            deleteTree(node->left);
+            deleteTree(node->right);
+            delete node;
+        }
+    }
 };
 
 int main() {
@@ -45,6 +54,9 @@ int main() {
     } else {
         cout << "The tree is not symmetric." << endl;
     }
+    // whenever you are allocating on the heap by using the new keyword you
+    // need to free that memory with the delete keyword
+    solution.deleteTree(root);
 
     return 0;
 }