1104. Path In Zigzag Labelled Binary Tree.cpp

1104. Path In Zigzag Labelled Binary Tree.cpp

@@ -0,0 +1,38 @@
+//Runtime: 0 ms, faster than 100.00% of C++ online submissions for Path In Zigzag Labelled Binary Tree.
+//Memory Usage: 8.5 MB, less than 100.00% of C++ online submissions for Path In Zigzag Labelled Binary Tree.
+
+class Solution {
+public:
+    vector<int> pathInZigZagTree(int label) {
+        int level = int(log2(label)); //index starts from 0
+        vector<int> path;
+        int node;
+        int index; //the index in a level, starts from 0, from left to right
+        path.push_back(label);
+
+        node = label;
+        while(node != 1){
+            if(level % 2 == 0){
+                //label from left to right
+                index = node - pow(2, level);
+                //get the index of its parent
+                index /= 2;
+                //pow(2, level) - 1: the 0th element of last level
+                // - index: because in the last level, label is from right to left
+                node = (pow(2, level) - 1) - index;
+            }else{
+                //label from right to left
+                //(pow(2, level)-1) - xxx: to change the direction of the index in a level
+                index = (pow(2, level)-1) - (node - pow(2, level));
+                //get the index of its parent
+                index /= 2;
+                node = pow(2, level-1) + index;
+            }
+            path.insert(path.begin(), node);
+            level--;
+            // cout << node << " ";
+        };
+
+        return path;
+    }
+};