Completed all the problems

Problem1.cpp

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+// Problem Name: level order traversal
+// Time Complexity : O(n)
+// Space Complexity : O(h) recursive stack space (height of the tree)
+// Did this code successfully run on Leetcode : yes
+// Any problem you faced while coding this : no
+
+// Your code here along with comments explaining your approach
+// 1. Here we can use any traversal, bfs or dfs
+// 2. Here we use dfs traversal, we keep resizing our answer vector to the
+// level, if they match
+// 3. Process the elements can be done inorder, postorder or preorder
+#include <bits/stdc++.h>
+using namespace std;
+
+/**
+ * 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:
+  vector<vector<int>> levelOrder(TreeNode *root) {
+    vector<vector<int>> res;
+    if (!root)
+      return res;
+    dfs(root, res, 0);
+    return res;
+  }
+
+  void dfs(TreeNode *root, vector<vector<int>> &res, int level) {
+    if (!root)
+      return;
+    if (res.size() == level) {
+      res.resize(level + 1);
+    }
+    dfs(root->left, res, level + 1);
+    dfs(root->right, res, level + 1);
+    res[level].push_back(root->val);
+  }
+};

Problem2.cpp

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+// Problem Name: Course schedule
+// Time Complexity : O(n)
+// Space Complexity : O(n)
+// Did this code successfully run on Leetcode : yes
+// Any problem you faced while coding this : no
+
+// Your code here along with comments explaining your approach
+// 1. Here we use topo sort to compute the independent courses first, by pushing
+// courses which have indegree of zero which means they are independent
+// 2. By using BFS, we decrease the indegree of each neighbor node, if it comes
+// to zero, we push to queue since they are now independent
+// 3. In the end we check if count == numCourses, we return true
+
+#include <bits/stdc++.h>
+using namespace std;
+
+class Solution {
+public:
+  bool canFinish(int numCourses, vector<vector<int>> &pre) {
+    vector<vector<int>> adj(numCourses);
+    vector<int> indegrees(numCourses, 0);
+    for (auto it : pre) {
+      adj[it[1]].push_back(it[0]);
+      indegrees[it[0]]++;
+    }
+
+    queue<int> q;
+    for (int i = 0; i < numCourses; i++) {
+      if (indegrees[i] == 0) {
+        q.push(i);
+      }
+    }
+
+    int count = 0;
+    while (!q.empty()) {
+      int front = q.front();
+      q.pop();
+      count++;
+      for (auto nei : adj[front]) {
+        indegrees[nei]--;
+        if (indegrees[nei] == 0) {
+          q.push(nei);
+        }
+      }
+    }
+    return count == numCourses;
+  }
+};