javascript多叉树的实现

1、创造一个节点

数据是以节点的形式存储的：

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class Node {
  constructor(data) {
    this.data = data;
    this.parent = null;
    this.children = [];
  }
}
2、创造树

树用来连接节点，就像真实世界树的主干一样，延伸着很多分支

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class MultiwayTree {
  constructor() {
    this._root = null;
  }
}
3、添加一个节点

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function add(data, toData, traversal) {
  let node = new Node(data)
  // 第一次添加到根节点
  // 返回值为this，便于链式添加节点
  if (this._root === null) {
    this._root = node;
    return this;
  }
  let parent = null,
    callback = function(node) {
      if (node.data === toData) {
        parent = node;
        return true;
      }
    };
  // 根据遍历方法查找父节点（遍历方法后面会讲到），然后把节点添加到父节点
  // 的children数组里
  // 查找方法contains后面会讲到
  this.contains(callback, traversal);
  if (parent) {
    parent.children.push(node);
    node.parent = parent;
    return this;
  } else {
    throw new Error(‘Cannot add node to a non-existent parent.‘);
  }
}
4、深度优先遍历

深度优先会尽量先从子节点查找，子节点查找完再从兄弟节点查找，适合数据深度比较大的情况，如文件目录

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function traverseDF(callback) {
  let stack = [], found = false;
  stack.unshift(this._root);
  let currentNode = stack.shift();
  while(!found && currentNode) {
    // 根据回调函数返回值决定是否在找到第一个后继续查找
    found = callback(currentNode) === true ? true : false;
    if (!found) {
      // 每次把子节点置于堆栈最前头，下次查找就会先查找子节点
      stack.unshift(...currentNode.children);
      currentNode = stack.shift();
    }
  }
}
5、广度优先遍历

广度优先遍历会优先查找兄弟节点，一层层往下找，适合子项较多情况，如公司岗位级别

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function traverseBF(callback) {
  let queue = [], found = false;
  queue.push(this._root);
  let currentNode = queue.shift();
  while(!found && currentNode) {
    // 根据回调函数返回值决定是否在找到第一个后继续查找
    found = callback(currentNode) === true ? true : false;
    if (!found) {
      // 每次把子节点置于队列最后，下次查找就会先查找兄弟节点
      queue.push(...currentNode.children)
      currentNode = queue.shift();
    }
  }
}
6、包含节点

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function contains(callback, traversal) {
  traversal.call(this, callback);
}
回调函数算法可自己根据情况实现，灵活度较高

7、移除节点

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// 返回被移除的节点
function remove(data, fromData, traversal) {
  let parent = null,
    childToRemove = null,
    callback = function(node) {
      if (node.data === fromData) {
        parent = node;
        return true;
      }
    };
  this.contains(callback, traversal);
  if (parent) {
    let index = this._findIndex(parent.children, data);
    if (index < 0) {
      throw new Error(‘Node to remove does not exist.‘);
    } else {
      childToRemove = parent.children.splice(index, 1);
    }
  } else {
    throw new Error(‘Parent does not exist.‘);
  }
  return childToRemove;
}
_findIndex实现:

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function _findIndex(arr, data) {
  let index = -1;
  for (let i = 0, len = arr.length; i < len; i++) {
    if (arr[i].data === data) {
      index = i;
      break;
    }
  }
  return index;
}
完整算法

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class Node {
  constructor(data) {
    this.data = data;
    this.parent = null;
    this.children = [];
  }
}
class MultiwayTree {
  constructor() {
    this._root = null;
  }
  //深度优先遍历
  traverseDF(callback) {
    let stack = [], found = false;
    stack.unshift(this._root);
    let currentNode = stack.shift();
    while(!found && currentNode) {
      found = callback(currentNode) === true ? true : false;
      if (!found) {
        stack.unshift(...currentNode.children);
        currentNode = stack.shift();
      }
    }
  }
  //广度优先遍历
  traverseBF(callback) {
    let queue = [], found = false;
    queue.push(this._root);
    let currentNode = queue.shift();
    while(!found && currentNode) {
      found = callback(currentNode) === true ? true : false;
      if (!found) {
        queue.push(...currentNode.children)
        currentNode = queue.shift();
      }
    }
  }
  contains(callback, traversal) {
    traversal.call(this, callback);
  }
  add(data, toData, traversal) {
    let node = new Node(data)
    if (this._root === null) {
      this._root = node;
      return this;
    }
    let parent = null,
      callback = function(node) {
        if (node.data === toData) {
          parent = node;
          return true;
        }
      };
    this.contains(callback, traversal);
    if (parent) {
      parent.children.push(node);
      node.parent = parent;
      return this;
    } else {
      throw new Error(‘Cannot add node to a non-existent parent.‘);
    }
  }
  remove(data, fromData, traversal) {
    let parent = null,
      childToRemove = null,
      callback = function(node) {
        if (node.data === fromData) {
          parent = node;
          return true;
        }
      };
    this.contains(callback, traversal);
    if (parent) {
      let index = this._findIndex(parent.children, data);
      if (index < 0) {
        throw new Error(‘Node to remove does not exist.‘);
      } else {
        childToRemove = parent.children.splice(index, 1);
      }
    } else {
      throw new Error(‘Parent does not exist.‘);
    }
    return childToRemove;
  }
  _findIndex(arr, data) {
    let index = -1;
    for (let i = 0, len = arr.length; i < len; i++) {
      if (arr[i].data === data) {
        index = i;
        break;
      }
    }
    return index;
  }
}
控制台测试代码

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var tree = new MultiwayTree();
tree.add(‘a‘)
  .add(‘b‘, ‘a‘, tree.traverseBF)
  .add(‘c‘, ‘a‘, tree.traverseBF)
  .add(‘d‘, ‘a‘, tree.traverseBF)
  .add(‘e‘, ‘b‘, tree.traverseBF)
  .add(‘f‘, ‘b‘, tree.traverseBF)
  .add(‘g‘, ‘c‘, tree.traverseBF)
  .add(‘h‘, ‘c‘, tree.traverseBF)
  .add(‘i‘, ‘d‘, tree.traverseBF);
console.group(‘traverseDF‘);
tree.traverseDF(function(node) {
  console.log(node.data);
});
console.groupEnd(‘traverseDF‘);
console.group(‘traverseBF‘);
tree.traverseBF(function(node) {
  console.log(node.data);
});
console.groupEnd(‘traverseBF‘);
// 深度优先查找
console.group(‘contains1‘);
tree.contains(function(node) {
  console.log(node.data);
  if (node.data === ‘f‘) {
    return true;
  }
}, tree.traverseDF);
console.groupEnd(‘contains1‘)
// 广度优先查找
console.group(‘contains2‘);
tree.contains(function(node) {
  console.log(node.data);
  if (node.data === ‘f‘) {
    return true;
  }
}, tree.traverseBF);
console.groupEnd(‘contains2‘);
tree.remove(‘g‘, ‘c‘, tree.traverseBF);