Pre-sequence traversal and middle sequence traversal tree construction two-fork tree

This problem is solved by recursive thinking, each time take the first element of the preface sequence as the root node of the current subtree, and then find the corresponding node in the sequence, in order to determine the root node corresponding to the Saozi right subtree of the sequence length, recursively constructs the root node Saozi right subtree.

TreeNode *execbuild (vector<int> &preorder, int prestart, int preend, vector<int> &inorder, int                Instart, int inend) {TreeNode *result = new TreeNode (Preorder[prestart]);        if (Prestart = = preend) {return result;        } int i;        for (i = instart; I <= inend; i++) {if (inorder[i] = = Preorder[prestart]) break;        } if (i = = Instart) {result---left = nullptr;        }else{Result--left = Execbuild (preorder, Prestart + 1, Prestart + I-instart, inorder, Instart, i-1);        } if (i = = inend) {result, right = nullptr;        }else{Result-right = Execbuild (preorder, Preend-(inend-i) + 1, preend, inorder, i + 1, inend);    } return result;         } TreeNode *buildtree (vector<int> &preorder, vector<int> &inorder) {//write your code here IntSize = Preorder.size ();                if (Size < 1) return nullptr;    Return Execbuild (preorder, 0, size-1, inorder, 0, size-1); }

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Pre-sequence traversal and middle sequence traversal tree construction two-fork tree