337. 打家劫舍 III

337. 打家劫舍 III

var rob = function(root) {
    function dfs(node) {
        if (!node) return [0, 0]; // [不偷当前节点的最大金额, 偷当前节点的最大金额]

        const left = dfs(node.left);
        const right = dfs(node.right);

        // 如果不偷当前节点，那么可以偷或不偷左右子节点
        const notRobCurrent = Math.max(left[0], left[1]) + Math.max(right[0], right[1]);

        // 如果偷当前节点，那么不能偷左右子节点
        const robCurrent = node.val + left[0] + right[0];

        return [notRobCurrent, robCurrent];
    }

    const result = dfs(root);
    return Math.max(result[0], result[1]);
};

function TreeNode(val, left, right) {
  this.val = val === undefined ? 0 : val;
  this.left = left === undefined ? null : left;
  this.right = right === undefined ? null : right;
}

function buildTree(preorder) {
  if (preorder.length === 0) return null;

  let root = new TreeNode(preorder[0]);
  let queue = [root];
  let i = 1;

  while (i < preorder.length) {
    let currentNode = queue.shift();

    if (preorder[i] !== null) {
      currentNode.left = new TreeNode(preorder[i]);
      queue.push(currentNode.left);
    }
    i++;

    if (i < preorder.length && preorder[i] !== null) {
      currentNode.right = new TreeNode(preorder[i]);
      queue.push(currentNode.right);
    }
    i++;
  }

  return root;
}
var rob = function (root) {
  if (!root) return 0;
  let evenSum = 0,
    oddSum = 0;
  function dfs(node, higt) {
    if (!node) return [0, 0]; //返回两个值：[偷当前节点的最大金额, 不偷当前节点的最大金额]
    // 递归计算左子树和右子树的最大金额
    let left = dfs(node.left, higt + 1);
    let right = dfs(node.right, higt + 1);
    // 如果偷当前节点，则不能偷其左右子节点
    const robThisNode = node.val + left[1] + right[1];
    // 如果不偷当前节点，则可以选择偷或不偷其左右子节点
    const notRobThisNode =
      Math.max(left[0], left[1]) + Math.max(right[0], right[1]);
    if (higt % 2 === 0) {
      evenSum = Math.max(robThisNode, notRobThisNode);
    } else {
      oddSum = Math.max(robThisNode, notRobThisNode);
    }
    // 返回当前节点偷和不偷的最大金额
    return [robThisNode, notRobThisNode];
  }
  dfs(root, 0);
  return Math.max(evenSum, oddSum);
};

// 构建二叉树
let preorder = [4, 1, null, 2, null, 3];
let root = buildTree(preorder);
console.log(rob(root));

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