Merge pull request #2785 from Abe0770/main

Create 0958-check-completeness-of-a-binary-tree.cpp

Author: felivalencia3

Diff for: cpp/0958-check-completeness-of-a-binary-tree.cpp

@@ -0,0 +1,49 @@
+/*
+  Given the root of a binary tree, determine if it is a complete binary tree.
+
+  In a complete binary tree, every level, except possibly the last, is completely filled,
+  and all nodes in the last level are as far left as possible. It can have between 1 and 2h
+  nodes inclusive at the last level h.
+
+  Ex. Input: root = [1,2,3,4,5,6]
+      Output: true
+      Explanation: Every level before the last is full (ie. levels with node-values {1} and {2, 3}), 
+      and all nodes in the last level ({4, 5, 6}) are as far left as possible.
+
+  Time  : O(N);
+  Space : O(N);
+*/
+
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    bool isCompleteTree(TreeNode* root) {
+        queue <TreeNode*> q;
+        q.push(root);
+        bool isNull = false;
+
+        while(!q.empty()) {
+            TreeNode * front = q.front();
+            if(!front)
+                isNull = true;
+            else {
+                if(isNull)
+                    return false;
+                q.push(front -> left);
+                q.push(front -> right);
+            }
+            q.pop();
+        }
+        return true;
+    }
+};