513. Find Bottom Left Tree Value

Author: amitbansal7

find-bottom-left-tree-value.cpp

@@ -0,0 +1,65 @@
+//Using level order traversal
+//Runtime: 9 ms
+class Solution {
+public:
+    int findBottomLeftValue(TreeNode* root) {
+        int res;
+        vector<int>temp;
+
+        queue<pair<int,TreeNode* > >Q;
+        Q.push(make_pair(1, root));
+        int maxlvl = 0;
+        while(!Q.empty())
+        {
+            pair<int, TreeNode* > t = Q.front();
+            Q.pop();
+
+            if(t.first > maxlvl)
+            {
+                maxlvl++;
+                if(temp.size() > 0)
+                {
+                    res = temp[0];
+                    temp.clear();
+                }
+            }
+            temp.push_back(t.second->val);
+
+            if(t.second->left)
+                Q.push(make_pair(t.first+1, t.second->left));
+
+            if(t.second->right)
+                Q.push(make_pair(t.first+1, t.second->right));
+        }
+
+        if(temp.size() > 0)
+            res = temp[0];
+
+        return res;
+    }
+};
+
+//Runtime: 9 ms
+//Better solution
+class Solution {
+public:
+    void solve(TreeNode* root, int lvl, pair<int,int> &res)
+    {
+        if(!root)
+            return;
+        solve(root->left, lvl+1, res);
+        solve(root->right, lvl+1, res);
+        if(lvl > res.first)
+        {
+            res.second = root->val;
+            res.first = lvl;
+        }
+    }
+
+    int findBottomLeftValue(TreeNode* root) {
+        pair<int,int>res;
+        res.first = res.second = 0;
+        solve(root, 1, res);
+        return res.second;
+    }
+};