在地图迭代中获取父索引

const tree = {
  id: 'root',
  children: [
    {
      id: 'child1',
      parent: 'root',
      children: [
        { id: 'grandchild1', parent: 'child1' },
        { id: 'grandchild2', parent: 'child1' }
      ]
    },
    {
      id: 'child2',
      parent: 'root',
      children: [
        { id: 'grandchild3', parent: 'child2' }
      ]
    }
  ]
};

function getParentIndex(nodeId, tree) {
  function traverse(node, parentId = null) {
    if (node.id === nodeId) return parentId;
    for (let child of node.children || []) {
      let result = traverse(child, node.id);
      if (result) return result;
    }
    return null;
  }
  return traverse(tree);
}

console.log(getParentIndex('grandchild1', tree)); // 输出: 'child1'

function getParentIndexIterative(nodeId, tree) {
  let stack = [{ node: tree, parentId: null }];
  while (stack.length > 0) {
    let { node, parentId } = stack.pop();
    if (node.id === nodeId) return parentId;
    for (let child of node.children || []) {
      stack.push({ node: child, parentId: node.id });
    }
  }
  return null;
}

console.log(getParentIndexIterative('grandchild1', tree)); // 输出: 'child1'