[leet] binary search tree + bk

Author: hyeonbinHur

허현빈/10주차/ Letter Combinations of a Phone Number.js

@@ -0,0 +1,36 @@
+/**
+ * @param {string} digits
+ * @return {string[]}
+ */
+var letterCombinations = function(digits) {
+    const obj ={
+        2: ['a','b','c'],
+        3: ['d','e','f'],
+        4: ['g','h','i'],
+        5: ['j','k','l'],
+        6: ['m','n','o'],
+        7: ['p','q','r','s'],
+        8: ['t','u','v'],
+        9: ['w','x','y','z']
+    }
+
+    const ans = [];
+    const bkArr = []
+    const bk = (digitCount) =>{
+        if(digitCount === digits.length){
+            ans.push(bkArr.join(""))
+            return
+        }
+        for(let i = 0 ; i< obj[digits[digitCount]].length;i++) {
+            bkArr[digitCount] = obj[digits[digitCount]][i]
+            bk(digitCount+1)
+        }
+    }
+    for(let i = 0 ;  i< obj[digits[0]].length; i++ ){
+        bkArr[0] = obj[digits[0]][i]
+        bk(1)
+ 
+    }
+   return ans
+};
+

허현빈/10주차/Invert Binary Tree.js

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+/**
+ * Definition for a binary tree node.
+ * function TreeNode(val, left, right) {
+ *     this.val = (val===undefined ? 0 : val)
+ *     this.left = (left===undefined ? null : left)
+ *     this.right = (right===undefined ? null : right)
+ * }
+ */
+/**
+ * @param {TreeNode} root
+ * @return {TreeNode}
+ */
+var invertTree = function(root) {
+  const swapChildren = (node) => {
+    const temp = node.left;
+    node.left = node.right;
+    node.right = temp;
+  };
+
+  const traverseTree = (node) => {
+    if (!node) return;
+
+    swapChildren(node);
+    traverseTree(node.left);
+    traverseTree(node.right);
+  };
+
+  traverseTree(root);
+  return root;
+};

허현빈/10주차/Maximum Depth of Binary Tree.js

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+/**
+ * @param {TreeNode} root
+ * @return {number}
+ */
+var maxDepth = function(root) {
+    const findDepth = (node, count) =>{
+        if(!node) return count
+        return Math.max(findDepth(node.left, count+1), findDepth(node.right, count+1))
+    }
+    return findDepth(root, 0)
+};