전차 범람과 중차 범람 트리 구조 두 갈래 트리 운행 결과 보기

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/**
 * Definition of TreeNode:
 * class TreeNode {
 * public:
 *     int val;
 *     TreeNode *left, *right;
 *     TreeNode(int val) {
 *         this->val = val;
 *         this->left = this->right = NULL;
 *     }
 * }
 */
 

class Solution {
    /**
     *@param preorder : A list of integers that preorder traversal of a tree
     *@param inorder : A list of integers that inorder traversal of a tree
     *@return : Root of a tree
     */
public:
    TreeNode *buildTree(vector<int> &preorder, vector<int> &inorder) {
        // write your code here
        int n = preorder.size();
	    if (n < 1)
	    {
		    return NULL;
	    }

	    return visit(preorder, 0, n-1, inorder, 0, n-1);
    }
private:
    TreeNode* visit(vector<int> &preorder, int left1, int right1, 
				vector<int> &inorder, int left2, int right2)
    {
	    if (left1 > right1)
	    {
		    return NULL;
	    }

	    if (left1 == right1)
	    {
		    return new TreeNode(preorder[left1]);
	    }

	    TreeNode *root = new TreeNode(preorder[left1]);
	    int i = left2;
	    for (; i <= right2; i++)
	    {
		    if (preorder[left1] == inorder[i])
		    {
			    break;
		    }
	    }

	    root->left = visit(preorder, left1+1, left1+i-left2, inorder, left2, i-1);
	    root->right = visit(preorder, left1+i-left2+1, right1, inorder, i+1, right2);

	    return root;
    }
};