Construct Binary Tree from In & Post: stack & recursive.

Author: DeanChensj

Medium/106_Construct-Binary-Tree-from-Inorder-and-Postorder-Traversal.cpp

@@ -0,0 +1,25 @@
+#include "../Header.h"
+
+using namespace std;
+ TreeNode* buildHelper(vector<int>& inorder, vector<int>& postorder, int il, int ir, int pl, int pr) {
+    if (pl > pr) return nullptr;
+    TreeNode *root = new TreeNode(postorder[pr]);
+    int i = il;
+    for (; i <= ir; i++) {
+        if (inorder[i] == postorder[pr]) break;
+    }
+    int t = pr-ir+i;
+    root->left = buildHelper(inorder, postorder, il, i-1, pl, t-1);
+    root->right = buildHelper(inorder, postorder, i+1, ir, t, pr-1);
+    return root;
+}
+
+TreeNode* buildTree(vector<int>& inorder, vector<int>& postorder) {
+    int sz = postorder.size() - 1;
+    return buildHelper(inorder, postorder, 0, sz, 0, sz);
+}
+
+int main(int argc, char const *argv[])
+{
+	return 0;
+}