添加(105.从前序与中序遍历序列构造二叉树):增加typescript版本

This commit is contained in:
Steve2020
2022-02-13 17:09:38 +08:00
parent bac5f8d70c
commit ddf79ac043

View File

@ -874,7 +874,51 @@ function buildTree(inorder: number[], postorder: number[]): TreeNode | null {
> 105.从前序与中序遍历序列构造二叉树 > 105.从前序与中序遍历序列构造二叉树
**新建数组:**
```typescript
function buildTree(preorder: number[], inorder: number[]): TreeNode | null {
if (preorder.length === 0) return null;
const rootVal: number = preorder[0];
const rootNode: TreeNode = new TreeNode(rootVal);
const rootValIndex: number = inorder.indexOf(rootVal);
rootNode.left = buildTree(preorder.slice(1, rootValIndex + 1), inorder.slice(0, rootValIndex));
rootNode.right = buildTree(preorder.slice(rootValIndex + 1), inorder.slice(rootValIndex + 1));
return rootNode;
};
```
**使用数组索引:**
```typescript
function buildTree(preorder: number[], inorder: number[]): TreeNode | null {
function recur(
preorder: number[], inorder: number[],
preBegin: number, preEnd: number,
inBegin: number, inEnd: number
): TreeNode | null {
if (preBegin === preEnd) return null;
const rootVal: number = preorder[preBegin];
const rootNode: TreeNode = new TreeNode(rootVal);
const rootValIndex: number = inorder.indexOf(rootVal, inBegin);
const leftPreBegin: number = preBegin + 1;
const leftPreEnd: number = preBegin + rootValIndex - inBegin + 1;
const leftInBegin: number = inBegin;
const leftInEnd: number = rootValIndex;
const rightPreBegin: number = leftPreEnd;
const rightPreEnd: number = preEnd;
const rightInBegin: number = rootValIndex + 1;
const rightInEnd: number = inEnd;
rootNode.left = recur(preorder, inorder, leftPreBegin, leftPreEnd, leftInBegin, leftInEnd);
rootNode.right = recur(preorder, inorder, rightPreBegin, rightPreEnd, rightInBegin, rightInEnd);
return rootNode;
};
return recur(preorder, inorder, 0, preorder.length, 0, inorder.length);
};
```
## C ## C