ConstructBinaryTreefromPreorderandInorderTraversal.java

src/ConstructBinaryTreefromPreorderandInorderTraversal.java

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+package Tree;
+/**
+ * 
+ * @author chenqun
+ * Given preorder and inorder traversal of a tree, construct the binary tree.
+ *
+ */
+public class ConstructBinaryTreefromPreorderandInorderTraversal {
+
+	public TreeNode buildTree(int[] preorder, int[] inorder){
+		if(preorder == null && inorder == null || preorder.length == 0) return null;
+		TreeNode root = new TreeNode(preorder[0]);
+		int i=0;
+		for(i=0;i<inorder.length;i++){
+			if(inorder[i] == preorder[0])
+				break;
+		}
+		//ÒÔiΪ·Ö½çµã
+		int[] new_inorder_left,new_inorder_right,new_preorder_left,new_preorder_right;
+		if(i < inorder.length){
+			new_inorder_left = new int[i];
+			System.arraycopy(inorder, 0, new_inorder_left, 0, i);
+			new_preorder_left = new int[i];
+			System.arraycopy(preorder, 1, new_preorder_left, 0, i);
+			root.left = buildTree(new_preorder_left,new_inorder_left);
+			new_inorder_right = new int[inorder.length-1-i];
+			System.arraycopy(inorder, 1+i, new_inorder_right, 0, inorder.length-1-i);
+			new_preorder_right = new int[preorder.length-1-i];
+			System.arraycopy(preorder, 1+i, new_preorder_right, 0, preorder.length-1-i);
+			root.right = buildTree(new_preorder_right,new_inorder_right);
+		}
+		return root;
+	}
+	public static void main(String[] args) {
+		// TODO Auto-generated method stub
+
+	}
+
+}