536 solved

536.cpp

@@ -0,0 +1,60 @@
+#include <iostream>
+#include <string>
+using namespace std;
+
+typedef struct node_ {
+    char c;
+    struct node_* left;
+    struct node_* right;
+} node;
+
+string inorder, preorder;
+int pidx;
+
+int find_node(int start, int end, char c) {
+    for (int i = start; i <= end; i++) {
+        if (inorder[i] == c)
+            return i;
+    }
+
+    return -1;
+}
+
+node* rebuild_tree(int start, int end) {
+    if (start > end) return NULL;
+
+    node* r = new node;
+    r->c = preorder[pidx++];
+    r->left = NULL;
+    r->right = NULL;
+
+    if (start == end)
+        return r;
+
+    int pos = find_node(start, end, r->c);
+
+    r->left = rebuild_tree(start, pos-1);
+    r->right = rebuild_tree(pos+1, end);
+
+    return r;
+}
+
+void print_postorder(node* r) {
+    if (r == NULL) return;
+
+    print_postorder(r->left);
+    print_postorder(r->right);
+
+    cout << r->c;
+}
+
+int main(void) {
+    while (cin >> preorder >> inorder) {
+        pidx = 0;
+        node* r = rebuild_tree(0, inorder.length()-1);
+        print_postorder(r);
+        cout << endl;
+    }
+
+    return 0;
+}