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  • leetcode: Construct Binary Tree from Inorder and Postorder Traversal

    /**
     * Definition for binary tree
     * struct TreeNode {
     *     int val;
     *     TreeNode *left;
     *     TreeNode *right;
     *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
     * };
     */
    class Solution {
    public:
        TreeNode *buildTree(vector<int> &inorder, vector<int> &postorder) {
            if( inorder.size() != postorder.size())
                return NULL;
            return core( inorder, 0, inorder.size()-1, postorder, 0, postorder.size()-1);
        }
        TreeNode *core( vector< int> &inorder, int left, int right, vector< int> &postorder, int start, int end){
            if( left > right || start > end)
                return NULL;
            TreeNode *root = new TreeNode( postorder[end]);
            int i = left;
            for( ; i <= right; ++i){
                if( inorder[i] == postorder[end])
                    break;
            }
            root->left = core( inorder, left, i-1, postorder, start, start+(i-left)-1);//这里要用下标减left,算offset。不然会数组越界
            root->right = core( inorder, i+1, right, postorder, start+(i-left), end-1);//这里要用下标减left。算offset,不然会数组越界
            return root;
        }
    };

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  • 原文地址:https://www.cnblogs.com/liguangsunls/p/7402822.html
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