Create Answer51.cpp

Answer51.cpp

@@ -0,0 +1,65 @@
+#include <bits/stdc++.h>
+
+using namespace std;
+struct Node {
+    int data;
+    Node *left, *right;
+};
+Node* newNode(int data);
+int search(int arr[], int start, int end, int value);
+Node* buildUtil(int in[], int post[], int inStrt, int inEnd, int* pIndex)
+{
+    if (inStart > inEnd)
+        return NULL;
+    Node* node = newNode(post[*pIndex]);
+    (*pIndex)--;
+    if (inStart == inEnd)
+        return node;
+    int iIndex = search(in, inStart, inEnd, node->data);
+    node->right = buildUtil(in, post, iIndex + 1, inEnd, pIndex);
+    node->left = buildUtil(in, post, inStart, iIndex - 1, pIndex);
+
+    return node;
+}
+Node* buildTree(int in[], int post[], int n)
+{
+    int pIndex = n - 1;
+    return buildUtil(in, post, 0, n - 1, &pIndex);
+}
+int search(int arr[], int start, int end, int value)
+{
+    int i;
+    for (i = start; i <= end; i++) {
+        if (arr[i] == value)
+            break;
+    }
+    return i;
+}
+Node* newNode(int data)
+{
+    Node* node = (Node*)malloc(sizeof(Node));
+    node->data = data;
+    node->left = node->right = NULL;
+    return (node);
+}
+void preOrder(Node* node)
+{
+    if (node == NULL)
+        return;
+    printf("%d ", node->data);
+    preOrder(node->left);
+    preOrder(node->right);
+}
+int main()
+{
+    int in[] = { 4, 8, 2, 5, 1, 6, 3, 7 };
+    int post[] = { 8, 4, 5, 2, 6, 7, 3, 1 };
+    int n = sizeof(in) / sizeof(in[0]);
+
+    Node* root = buildTree(in, post, n);
+
+    cout << "Preorder of the constructed tree : \n";
+    preOrder(root);
+
+    return 0;
+}