Construct Binary Tree from Preorder and Postorder Traversal

// Accepted solution for LeetCode #889: Construct Binary Tree from Preorder and Postorder Traversal
/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode() {}
 *     TreeNode(int val) { this.val = val; }
 *     TreeNode(int val, TreeNode left, TreeNode right) {
 *         this.val = val;
 *         this.left = left;
 *         this.right = right;
 *     }
 * }
 */
class Solution {
    private Map<Integer, Integer> pos = new HashMap<>();
    private int[] preorder;

    public TreeNode constructFromPrePost(int[] preorder, int[] postorder) {
        this.preorder = preorder;
        for (int i = 0; i < postorder.length; ++i) {
            pos.put(postorder[i], i);
        }
        return dfs(0, preorder.length - 1, 0, postorder.length - 1);
    }

    private TreeNode dfs(int a, int b, int c, int d) {
        if (a > b) {
            return null;
        }
        TreeNode root = new TreeNode(preorder[a]);
        if (a == b) {
            return root;
        }
        int i = pos.get(preorder[a + 1]);
        int m = i - c + 1;
        root.left = dfs(a + 1, a + m, c, i);
        root.right = dfs(a + m + 1, b, i + 1, d - 1);
        return root;
    }
}

// Accepted solution for LeetCode #889: Construct Binary Tree from Preorder and Postorder Traversal
/**
 * Definition for a binary tree node.
 * type TreeNode struct {
 *     Val int
 *     Left *TreeNode
 *     Right *TreeNode
 * }
 */
func constructFromPrePost(preorder []int, postorder []int) *TreeNode {
	pos := map[int]int{}
	for i, x := range postorder {
		pos[x] = i
	}
	var dfs func(int, int, int, int) *TreeNode
	dfs = func(a, b, c, d int) *TreeNode {
		if a > b {
			return nil
		}
		root := &TreeNode{Val: preorder[a]}
		if a == b {
			return root
		}
		i := pos[preorder[a+1]]
		m := i - c + 1
		root.Left = dfs(a+1, a+m, c, i)
		root.Right = dfs(a+m+1, b, i+1, d-1)
		return root
	}
	return dfs(0, len(preorder)-1, 0, len(postorder)-1)
}

# Accepted solution for LeetCode #889: Construct Binary Tree from Preorder and Postorder Traversal
# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
class Solution:
    def constructFromPrePost(
        self, preorder: List[int], postorder: List[int]
    ) -> Optional[TreeNode]:
        def dfs(a: int, b: int, c: int, d: int) -> Optional[TreeNode]:
            if a > b:
                return None
            root = TreeNode(preorder[a])
            if a == b:
                return root
            i = pos[preorder[a + 1]]
            m = i - c + 1
            root.left = dfs(a + 1, a + m, c, i)
            root.right = dfs(a + m + 1, b, i + 1, d - 1)
            return root

        pos = {x: i for i, x in enumerate(postorder)}
        return dfs(0, len(preorder) - 1, 0, len(postorder) - 1)

// Accepted solution for LeetCode #889: Construct Binary Tree from Preorder and Postorder Traversal
struct Solution;
use rustgym_util::*;

impl Solution {
    fn construct_from_pre_post(pre: Vec<i32>, post: Vec<i32>) -> TreeLink {
        Self::build(&mut 0, &mut 0, &pre, &post)
    }

    fn build(i: &mut usize, j: &mut usize, pre: &[i32], post: &[i32]) -> TreeLink {
        let val = pre[*i];
        *i += 1;
        let mut left = None;
        let mut right = None;
        if val != post[*j] {
            left = Self::build(i, j, pre, post);
        }
        if val != post[*j] {
            right = Self::build(i, j, pre, post);
        }
        *j += 1;
        tree!(val, left, right)
    }
}

#[test]
fn test() {
    let pre = vec![1, 2, 4, 5, 3, 6, 7];
    let post = vec![4, 5, 2, 6, 7, 3, 1];
    let res = tree!(
        1,
        tree!(2, tree!(4), tree!(5)),
        tree!(3, tree!(6), tree!(7))
    );
    assert_eq!(Solution::construct_from_pre_post(pre, post), res);
}

// Accepted solution for LeetCode #889: Construct Binary Tree from Preorder and Postorder Traversal
/**
 * Definition for a binary tree node.
 * class TreeNode {
 *     val: number
 *     left: TreeNode | null
 *     right: TreeNode | null
 *     constructor(val?: number, left?: TreeNode | null, right?: TreeNode | null) {
 *         this.val = (val===undefined ? 0 : val)
 *         this.left = (left===undefined ? null : left)
 *         this.right = (right===undefined ? null : right)
 *     }
 * }
 */

function constructFromPrePost(preorder: number[], postorder: number[]): TreeNode | null {
    const pos: Map<number, number> = new Map();
    const n = postorder.length;
    for (let i = 0; i < n; ++i) {
        pos.set(postorder[i], i);
    }
    const dfs = (i: number, j: number, n: number): TreeNode | null => {
        if (n <= 0) {
            return null;
        }
        const root = new TreeNode(preorder[i]);
        if (n === 1) {
            return root;
        }
        const k = pos.get(preorder[i + 1])!;
        const m = k - j + 1;
        root.left = dfs(i + 1, j, m);
        root.right = dfs(i + 1 + m, k + 1, n - 1 - m);
        return root;
    };
    return dfs(0, 0, n);
}