Question

旅行的形式为[旅行的起点，旅行的目的地]。您会以随机顺序获得行程。编写Javascript函数以找出旅程的起点。用户也可以输入参观的地方。

示例1： exampleTrips：= [ [A,B], [B,C], [C,D] ] 此示例中的行程始于"A"。

示例2： exampleTrips：= [ [D,E], [F,D], [E,X] ] 此示例中的行程始于"F"。

定义一个数组将其拆分为两个数组a1和a2 找到b / w a1和a2之差从a1返回剩余元素

var a = [ ['a', 'b'], ['b', 'c'], ['c', 'd'], ['e', 'a'] ];

var a1 = a.map(function(tuple) {
  return tuple[0];
});

var a2 = a.map(function(tuple) {
  return tuple[1];
});

function difference(a1, a2) {
  var result = [];
  for (var i = 0; i < a1.length; i++) {
    if (a2.indexOf(a1[i]) === -1) {
      result.push(a1[i]);
    }
  }
  return result;
}

console.log(difference(a1, a2));

Answer 1

首先，获取开始和结束（仅非重复元素），然后找出哪个是数组中的第一个元素：

const a = [['a','b'], ['b','c'],['d','a']];
const startEnd = a.reduce((acc, curr) => acc.concat(curr)).filter((e, i, arr) => arr.indexOf(e) == arr.lastIndexOf(e));
const res = a.findIndex(([e]) => startEnd.includes(e));
console.log(res);

Answer 2

我有类似的面试问题，这是我的答案：

input {
    udp  {
        type => "dhcp"
        port => "518"
    }
}

filter {
    if [type] == "dhcp" {
        grok {
            match => {"message" => "assigned"}
        }
    }
}

output {
    if [type] == "dhcp" and "_grokparsefailure" not in [tags] {
        elasticsearch { 
            hosts => ["localhost:9200"] 
            index => "dhcp-%{+yyyy.MM.dd}-001"
        }
    }
}

Answer 3

问题中的解决方案是O（n ²）

您可以在O（n）中使用哈希图进行

const findStartingPoint = (trips) => {
    // create a hash map of starting points from all trips
    const tripStarts = trips.reduce((acc, trip) => {
        acc[trip[0]] = false
        return acc
    }, {}) 
    // get ending points from all trips
    const tripEnds = trips.map(trip => trip[1])
    tripEnds.forEach(end => {
        tripStarts[end] = true
    });
    // get tripStarts - tripEnds
    // I'm assuming a journey means continuous trips. This means Every start 
    // except for the journey start should be in trip ends
    let start
    Object.keys(tripStarts).forEach(tripKey => {
        if(tripStarts[tripKey] === false) {
            start = tripKey
        }
    })
    return start ? start : 'You can start your trip anywhere'
}

console.log(findStartingPoint([['Cologne','Berlin'],['Munich','Cologne'],['YourPlace','Munich']]))
console.log(findStartingPoint(
    [
        ['Cologne','Berlin'],
        ['Munich','Cologne'],
        ['YourPlace','Munich']
    ]) === 'YourPlace')

console.log(findStartingPoint(
    [ ['A','B'], ['B','C'], ['C','D'] ]) === 'A')

console.log(findStartingPoint(
    [ ['D','E'], ['F','D'], ['E','X'] ]) === 'F')

console.log(findStartingPoint(
    [ ['A','B'], ['B','C'], ['C','D'], ['D', 'A']]) === 'You can start your trip anywhere')

用于找出旅行/旅程起点的功能

3 个答案: