Merge pull request DaleStudy#80 from nhistory/week3

[Sehwan] Week3 solutions with javascript

Author: SamTheKorean

climbing-stairs/nhistory.js

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+/**
+ * @param {number} n
+ * @return {number}
+ */
+var climbStairs = function (n) {
+  // Make an array to store each number of ways
+  let steps = new Array(n);
+  // When stairs is 1 and 2 has exact number 1 and 2
+  steps[1] = 1;
+  steps[2] = 2;
+  // Iterate to get ways of 3 more steps stairs
+  // ((n-1) + (n-2))
+  for (let i = 3; i <= n; i++) {
+    steps[i] = steps[i - 1] + steps[i - 2];
+  }
+  return steps[n];
+};
+
+// TC: O(n)
+// SC: O(n)

maximum-depth-of-binary-tree/nhistory.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 {number}
+ */
+var maxDepth = function (root) {
+  // Check root is null or not
+  if (root === null) {
+    return 0;
+  }
+  // Make queue array to store root and depth variable
+  let queue = [root];
+  let depth = 0;
+  // Iterate until there is an element inside of queue
+  while (queue.length > 0) {
+    // Record level size to avoid fault size measuring
+    let levelSize = queue.length;
+
+    for (let i = 0; i < levelSize; i++) {
+      // Grasp first element from the queue
+      const node = queue.shift();
+      // Push the left node into the queue
+      if (node.left) {
+        queue.push(node.left);
+      }
+      // Push the right node into the queue
+      if (node.right) {
+        queue.push(node.right);
+      }
+    }
+    // Increase depth value
+    depth++;
+  }
+
+  return depth;
+};
+
+// TC: O(n)
+// SC: O(n)

meeting-rooms/nhistory.js

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+/**
+ * Definition of Interval:
+ * class Interval {
+ *   constructor(start, end) {
+ *     this.start = start;
+ *     this.end = end;
+ *   }
+ * }
+ */
+
+class Solution {
+  /**
+   * @param {Interval[]} intervals
+   * @returns {boolean}
+   */
+  canAttendMeetings(intervals) {
+    // Sort the intervals based on their start times
+    intervals.sort((a, b) => a.start - b.start);
+
+    for (let i = 0; i < intervals.length - 1; i++) {
+      // Check if the current interval overlaps with the next interval
+      if (intervals[i].end > intervals[i + 1].start) {
+        return false;
+      }
+    }
+
+    return true;
+  }
+}
+
+// TC: O(nlogn)
+// SC: O(1)

same-tree/nhistory.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} p
+ * @param {TreeNode} q
+ * @return {boolean}
+ */
+var isSameTree = function (p, q) {
+  // If p and q is null, return true
+  if (!p && !q) return true;
+  // Compare root and length between p and q
+  if (!p || !q || p.val !== q.val) return false;
+  // Execute recursive function to search each tree
+  return isSameTree(p.left, q.left) && isSameTree(p.right, q.right);
+};
+
+// TC: O(n)
+// SC: O(n)

subtree-of-another-tree/nhistory.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
+ * @param {TreeNode} subRoot
+ * @return {boolean}
+ */
+var isSubtree = function (root, subRoot) {
+  // Make function to check two triangle is same or not
+  const isSame = (root1, root2) => {
+    // If both of root1 and root2 is null, return true
+    if (!root1 && !root2) return true;
+    // If one of root1 and root2 is null or root1.val is not equal to root2.val, return false
+    if (!root1 || !root2 || root1.val !== root2.val) return false;
+    // Compare each left and right value with recursive
+    return isSame(root1.left, root2.left) && isSame(root1.right, root2.right);
+  };
+
+  // Make dfs function to check nodes inside of root tree
+  const dfs = (node) => {
+    // if node is null, return false
+    if (!node) return false;
+    // Check triangle is equal to subRoot
+    if (isSame(node, subRoot)) return true;
+    // Check one of the left or right node is same with triangle
+    return dfs(node.left) || dfs(node.right);
+  };
+  // Execute dfs function
+  return dfs(root);
+};
+
+// TC: O(n*m)
+// SC: O(max(m,n))