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  • 44: Construct Binary Tree from Inorder and Postorder Traversal

     /************************************************************************/
                /*       44:  Construct Binary Tree from Inorder and Postorder Traversal                            */
                /************************************************************************/
                /*
                 * Given inorder and postorder traversal of a tree, construct the binary tree.
                 *
                 * Note:
    You may assume that duplicates do not exist in the tree.
                 * */
                
                /*** 递归做法******************/
                /*
                 * 问题:
                 *
                 * 1: 给出 中序与后序,是否能唯一确定一棵二叉树?(在没有重复节点值的情况下)?
                 * 2:  给出 中序与前序,是否能唯一确定一棵二叉树?(在没有重复节点值的情况下)?
                 * 自己测试了,出现了不能唯一确定一棵树的情况,待检测
                 * */
             

      public TreeNode buildTreeByPost_In(int[] inorder, int[] postorder)
                {
                     TreeNode root=null;
                    
                     root=helper_PostAndIn(postorder.length-1,0,postorder.length-1,postorder,inorder);
                        return root;
                }
                
                private  TreeNode helper_PostAndIn(int PostStart, int inStart, int inEnd, int[] postorder, int[] inorder) {
                      if (PostStart < 0 || inStart > inEnd) {
                            return null;
                        }
                        TreeNode root = new TreeNode(postorder[PostStart]);
                        int inIndex = 0; // Index of current root in inorder
                        for (int i = inStart; i <= inEnd; i++) {
                            if (inorder[i] == root.val) {
                                inIndex = i;
                                break;
                            }
                        }
                        root.right = helper_PostAndIn(PostStart-1, inIndex + 1, inEnd, postorder, inorder);
                        root.left = helper_PostAndIn(PostStart-(inEnd-inIndex+1), inStart, inIndex - 1, postorder, inorder);
                        return root;
                }
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  • 原文地址:https://www.cnblogs.com/theonemars/p/4254340.html
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