判断是否是回文
function checkBack(str){
return str==str.split("").reverse().join("");
}
console.log(checkBack("ava"));
console.log(checkBack("avaa"));
数组去重
function onlySet(arr){
var res=[];
arr.map(function(data){
if(res.indexOf(data)===-1){
res.push(data);
}
})
return res;
}
console.log(onlySet([1,13,24,11,11,14,1,2]));
统计一个字符串出现最多的字母
function countMost(str){
if(str.length===1) return str;
var count=[];
for(var i=0;i
引申为数组
排序算法 (冒泡,快速)
//不借助临时变量,进行两个整数的交换
//es6
function swap(a,b){
return [b,a];
}
console.log(swap(1,2));
//usually
function swap2(a,b){
a=b+a; //想让一个等于总和
b=a-b;
a=a-b;
return [a,b];
}
console.log(swap2(1,2));
生成斐波那契数组的方法
找出下列正数组的最大差值比如
function getMax(arr){
return Math.max.apply(null,arr)-Math.min.apply(null,arr);
}
console.log(getMax([100,5,11,7,8,9]));
随机生成指定长度的字符串
function randomStr(n){
var str="qwertyuiopasdfghjklzxcvbnmQWERTYUIOPASDFGHJKLZXCVBNM1234567890";
var t="";
for(var i=0;i
二叉查找树
//在写的时候需要足够理解二叉搜素树的特点,需要先设定好每个节点的数据结构
class Node {
constructor(data, left, right) {
this.data = data;
this.left = left;
this.right = right;
}
}
//树是有节点构成,由根节点逐渐延生到各个子节点,因此它具备基本的结构就是具备一个根节点,具备添加,查找和删除节点的方法.
class BinarySearchTree {
constructor() {
this.root = null;
}
insert(data) {
let n = new Node(data, null, null);
if (!this.root) {
return this.root = n;
}
let currentNode = this.root;
let parent = null;
while (1) {
parent = currentNode;
if (data < currentNode.data) {
currentNode = currentNode.left;
if (currentNode === null) {
parent.left = n;
break;
}
} else {
currentNode = currentNode.right;
if (currentNode === null) {
parent.right = n;
break;
}
}
}
}
remove(data) {
this.root = this.removeNode(this.root, data)
}
removeNode(node, data) {
if (node == null) {
return null;
}
if (data == node.data) {
// no children node
if (node.left == null && node.right == null) {
return null;
}
if (node.left == null) {
return node.right;
}
if (node.right == null) {
return node.left;
}
let getSmallest = function(node) {
if(node.left === null && node.right == null) {
return node;
}
if(node.left != null) {
return node.left;
}
if(node.right !== null) {
return getSmallest(node.right);
}
}
let temNode = getSmallest(node.right);
node.data = temNode.data;
node.right = this.removeNode(temNode.right,temNode.data);
return node;
} else if (data < node.data) {
node.left = this.removeNode(node.left,data);
return node;
} else {
node.right = this.removeNode(node.right,data);
return node;
}
}
find(data) {
var current = this.root;
while (current != null) {
if (data == current.data) {
break;
}
if (data < current.data) {
current = current.left;
} else {
current = current.right
}
}
return current.data;
}
}
获取指定范围内的随机数
function getRandom(min,max){
//return Math.floor(Math.random() * (max - min + 1)) + min;
return min+Math.round(Math.random()*(max-min));
}
console.log(getRandom(0,10));
随机获取数组中的元素
function getRandomArr(arr){
return arr[Math.floor(Math.random()*arr.length)];
}
console.log(getRandomArr([1,2,3]));
打乱数字数组的顺序
function shuffle(arr){
return arr.sort(function(){
return Math.random()-0.5;
})
}
console.log(shuffle([1,2,3,4]));
保留指定小数位
var num =4.345678;
num = num.toFixed(4);
console.log(num);
折半
function binarySearch(des, arr) {
if (!(arr instanceof Array))
return "arr is not array";
var low = 0;
var high = arr.length;
var mid;
while (low <= high) {
mid = Math.floor((low + high) / 2);
if (arr[mid] < des) {
low = mid + 1;
} else if (arr[mid] > des) {
high = mid - 1;
} else {
return mid;
}
}
return 0;
}
冒泡
function bubbleSort(arr) {
if (!(arr instanceof Array))
return "arr is not array";
var flag = true;
for (var i = 0; i < arr.length - 1 && flag; i++) {
flag = false;
for (var j = arr.length - 1; j >= i; j--) {
if (arr[j] < arr[j - 1]) {
var temp = arr[j];
arr[j] = arr[j - 1];
arr[j - 1] = temp;
flag = true;
}
}
}
return arr;
}
快排
function qsort(arr, low, high) {
var pivot;
if (low < high) {
pivot = Partition(arr, low, high)
this.qsort(arr, low, pivot - 1);
this.qsort(arr, pivot + 1, high)
}
}
function Partition(arr, low, high) {
var pivotkey = arr[low];
while (low < high) {
while (low < high && arr[high] >= pivotkey)
high--;
swap(arr, low, high)
while (low < high && arr[low] <= pivotkey)
low++;
swap(arr, low, high)
}
return low;
}
function quickSort(arr) {
if (!(arr instanceof Array))
return "arr is not array";
this.qsort(arr, 0, arr.length - 1);
return arr;
}