关于一些算法
来源：互联网 发布：单片机晶振电路 编辑：程序博客网 时间：2024/05/16 18:27
1 先说下递归吧，有关 100 步梯级，每次走一到三步，求有多少走法？
一开始用枚举，例如算出走了 3*33 +1，然后求出其排列组合，这样搞得头都大
下面是正确的思路，但问题是递归太多
<!DOCTYPE html><html lang="en"><head><meta charset="UTF-8"><title>Document</title><script>var steps = [];function getSteps(n){if(n==1){return 1;}if(n==2){return 2;}if(n==3){return 4}return arguments.callee(n-1)+arguments.callee(n-2)+arguments.callee(n-3);}console.log(getSteps(10))</script></head><body></body></html>下面是优化版本
<!DOCTYPE html><html lang="en"><head><meta charset="UTF-8"><title>Document</title><script>var steps = [];function getSteps(n){for(var i = 0; i< n; i++){switch(i){case 0 : steps[i] = 1;break;case 1 : steps[i] = 2;break;case 2 : steps[i] = 4;break;default: steps[i] = steps[i-1]+steps[i-2]+steps[i-3];}}return steps[i-1]}console.log(getSteps(100))</script></head><body></body></html>2 排列组合算法，如求var arr =['A','B','c','D']; 取两个有多少种方法，
（1） 用树分法
<!DOCTYPE HTML><html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"><title>无标题文档</title><style></style><script>var arr =['A','B','c','D'];function show(arr,num){var resultNum = 0;var iNow = 1;if(num ==1){return resultNum = arr.length;}function change(arr,iNow){for(var i = 0; i< arr.length; i++){var result = arr.concat();result.splice(i,1);if( num == iNow){resultNum += result.length}else{change(result,iNow+1);}}}change(arr,iNow+1);return resultNum;}var a = show(arr,1);console.log(a);</script></head><body></body></html>（2）用数学的方法，A4取2之类的<!DOCTYPE HTML><html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"><title>无标题文档</title><style></style><script>function A(n,m){return f(n)/f(n-m)}function C(n,m){return f(n)/f(n-m)/f(m)}function f(n){if(n==1){return 1;}return n*f(n-1)}var a = A(4,2);console.log(a);var b = C(4,3);console.log(b);</script></head><body></body></html>3 矩形数组的行列变换
<!doctype html><html><head lang="zh"> <meta charset="utf-8"> <title>灵域</title> <meta name="renderer" content="webkit"> <script> window.onload = function(){ var oList = document.querySelector('#list'); var aLi = oList.getElementsByTagName('li'); var size = 4; var sizeGrid = 50; var arr = []; oList.style.width = (size*(sizeGrid+1) + 1) +'px'; oList.style.height = (size*(sizeGrid+1) + 1) +'px'; for(var i=0; i< size*size; i++){ var oLi = document.createElement('li'); oLi.style.width = sizeGrid+'px'; oLi.style.height = sizeGrid +'px'; oLi.innerHTML = i ; arr.push(i); oList.appendChild(oLi); } function changeXY(arr,size){ var newArr =[]; var iNow = 0; (function(){ if(iNow == size){ return ; } for(var i =0;i<arr.length; i++){ if(i%size == iNow){ newArr.push(arr[i]); } } iNow ++; arguments.callee(); })() return newArr; } arr = changeXY(arr,size); for(var i = 0; i< arr.length; i++){ aLi[i].innerHTML = arr[i]; } } </script> <style>*{padding:0; margin:0;}#list{border-left: 1px solid #000; border-top: 1px solid #000;}#list li{float:left;border-right: 1px solid #000; border-bottom: 1px solid #000;}li{list-style: none}</style></head><body ><ul id="list"></ul></body></html>可应于消i消乐的游戏，每行每列出现三个就消除<!doctype html><html><head lang="zh"> <meta charset="utf-8"> <title>灵域</title> <meta name="renderer" content="webkit"> <script> window.onload = function(){ var oList = document.querySelector('#list'); var aLi = oList.getElementsByTagName('li'); var size = 7; var sizeGrid = 70; var arr = []; oList.style.width = (size*sizeGrid) +'px'; oList.style.height = (size*sizeGrid) +'px'; for(var i=0; i< size*size; i++){ var oLi = document.createElement('li'); oLi.style.width = sizeGrid+'px'; oLi.style.height = sizeGrid +'px'; oLi.className = 'box'+Math.floor(Math.random()*6); arr.push(i); oList.appendChild(oLi); } findElem(); function findElem(){ var arr = []; function addArr(aLi){ var preLi = aLi[0]; var iNum = 0; for(var i = 0; i<aLi.length; i++){ if(preLi.className == aLi[i].className && i%size != 0){ iNum ++; }else{ if(iNum >= 2){ for(var j = 0; j<=iNum; j++){ if(toCon(aLi[(i-1)-j])){ arr.unshift(aLi[(i-1)-j]); } } } iNum = 0; } preLi = aLi[i] } } function toCon(li){ for(var i=0; i<arr.length;i++){ if(arr[i] == li){ return false } } return true; } addArr(aLi); addArr(changeXY(aLi,size)); for(var i = 0; i<aLi.length;i++){ aLi[i].style.opacity = 0.3; } for(var i = 0; i<arr.length;i++){ arr[i].style.opacity = 1; } } function changeXY(arr,size){ var newArr =[]; var iNow = 0; (function(){ if(iNow == size){ return ; } for(var i =0;i<arr.length; i++){ if(i%size == iNow){ newArr.push(arr[i]); } } iNow ++; arguments.callee(); })() return newArr; } } </script> <style>*{padding:0; margin:0;}#list{margin: 20px auto; background:#000;}#list li{float:left;}#list li.box0{background: url(img/1.jpg);}#list li.box1{background: url(img/2.jpg);}#list li.box2{background: url(img/3.jpg);}#list li.box3{background: url(img/4.jpg);}#list li.box4{background: url(img/5.jpg);}#list li.box5{background: url(img/6.jpg);}li{list-style: none}</style></head><body ><ul id="list"></ul></body></html>接着就是螺旋矩阵
<!DOCTYPE HTML><html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"><title>无标题文档</title><style>*{ margin:0; padding:0;}li{ list-style:none;}#ul1{ margin:20px auto; border:1px #FFF solid; border-bottom:none; border-right:none; overflow:hidden; background-image:url(img/bg.jpg); background-size:cover;}#ul1 li{ float:left; border:1px #FFF solid; border-top:none; border-left:none; background-size:cover;}#ul1 li.active{ animation:0.5s linear infinite flash; -webkit-animation:0.5s linear infinite flash;}@keyframes flash{0%{ opacity:0.1;}50%{ opacity:1;}100%{ opacity:0.1;}}@-webkit-keyframes flash{0%{ opacity:0.1;}50%{ opacity:1;}100%{ opacity:0.1;}}</style></head><body><ul id="ul1"></ul><script>var oUl = document.getElementById('ul1');var aLi = oUl.getElementsByTagName('li');var size = 8;var len = size * size;var sizeGird = 50;var row = 0;var col = 0;var min = 0;var max = size - 1;var arr = [];var bgArr = [];oUl.style.width = size * (sizeGird + 1) + 'px';for(var i=0;i<len;i++){var oLi = document.createElement('li');oLi.style.width = sizeGird + 'px';oLi.style.height = sizeGird + 'px';oUl.appendChild(oLi);}for(var i=0;i<len;i++){//aLi[ row * size + col ].innerHTML = i;arr.push( aLi[ row * size + col ] );if( row == min && col < max ){col = col + 1;}else if( col == max && row < max ){row = row + 1;}else if( row == max && col > min ){col = col - 1;}else if( col == min && row > min ){row = row - 1;}if( row - 1 == min && col == min ){min = min + 1;max = max - 1;}}for(var i=0;i<aLi.length;i++){if(i%5==0){var bgImage = 'url(img/'+ ( Math.floor(Math.random()*11+1) ) +'.jpg)';arr[i].style.backgroundImage = bgImage;bgArr.push([i,bgImage]);}}run();setInterval(run,1000);function run(){for(var i=0;i<aLi.length;i++){aLi[i].style.backgroundImage = '';aLi[i].className = '';}for(var i=0;i<bgArr.length;i++){bgArr[i][0] = bgArr[i][0] + 1;if(arr[ bgArr[i][0] ]){arr[ bgArr[i][0] ].style.backgroundImage = bgArr[i][1];arr[ bgArr[i][0] ].className = 'active';arr[ bgArr[i][0] ].style.animationDelay = -Math.random()*2 + 's';arr[ bgArr[i][0] ].style.webkitAnimationDelay = -Math.random()*2 + 's';}else{bgArr.pop();var bgImage = 'url(img/'+ ( Math.floor(Math.random()*11+1) ) +'.jpg)';bgArr.unshift([0,bgImage]);}}}</script></body></html>打乱数组的算法
Array.prototype.shuffle = function(){var input = this;for(var i = this.length-1;i>=0; i--){var randomIndex = Math.floor(Math.random()*(i+1));var value = input[randomIndex];input[randomIndex] = input[i];input[i] = value;}return input;}var arr = [1,2,3,4,5,6,7]var t = arr.shuffle();console.log(t);<pre name="code" class="html">还有就是这样arr.sort(function(){return Math.random() - 0.5;})判断字符串是否回文
<!doctype html><html><head lang="zh"> <meta charset="utf-8"> <title>灵域</title> <meta name="renderer" content="webkit"> <script> var str = 'abc dcba'; function fn(str){ str = str.replace(/\W/g,''); // 去掉空格类的 var str2 = str.split('').reverse().join(''); if(str == str2){ return true; }else{ return false; } } console.log(fn(str)); console.log(fn('abcb')); function fn2(str){ str = str.replace(/\W/g,''); var len = str.length; var halfLen = Math.floor(len/2); for(var i= 0; i<halfLen; i++){ if(str[i]!=str[len-1-i]){ return false } } return true } console.log(fn2(str)); console.log(fn2('abcb')); </script></body></html><!DOCTYPE html><html> <head> <title></title> </head> <body> </body></html><html lang="en"> <head> <meta charset="UTF-8"> <title>Document</title> <style> *{padding: 0; margin: 0;} body{text-align: center;} li{ list-style: none;} ul{margin: 30px auto 0px; border:1px solid #000; border-bottom: none; border-right: none;} li{border:1px solid #000; border-top:none; border-left: 0; float: left;} .sty1{background: green;} .sty2{background: blue;} .sty3{background: red;} #input1{margin: 10px auto;} </style> <script> window.onload = function(){ var oUl = document.getElementById('ul1'); var aLi = oUl.getElementsByTagName('li'); var oBtn = document.getElementById('input1'); var beginLi = oUl.getElementsByClassName('sty1');var endLi = oUl.getElementsByClassName('sty3'); var gridSize =20; var openArr =[]; var closeArr =[]; var map =[0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,2,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,2,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,2,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,2,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,2,0,0,3,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0 ]; init(); function init(){ createMap(); oBtn.onclick=function(){ openFn(); } } function createMap(){ oUl.style.width= Math.sqrt(map.length)*(gridSize+1)+'px'; oUl.style.height= Math.sqrt(map.length)*(gridSize+1)+'px'; for(var i=0; i<map.length;i++){ var oLi = document.createElement('li'); oLi.style.width = gridSize+'px'; oLi.style.height = gridSize+'px'; oUl.appendChild(oLi); if(map[i]==1){ oLi.className = 'sty1'; openArr.push(oLi); } if(map[i]==2){ oLi.className = 'sty2'; closeArr.push(oLi); } if(map[i]==3){ oLi.className = 'sty3'; } } } function openFn(){ var nowLi = openArr.shift(); if( nowLi == endLi[0] ){showLine();//console.log(1)return;} closeFn(nowLi); findLi(nowLi); openArr.sort(function(li1,li2){return li1.num - li2.num;});openFn(); } function closeFn(li){ closeArr.push(li) } function findLi(nowLi){ var arr=[]; for(var i=0; i< aLi.length;i++){ if(filter(aLi[i])){ arr.push(aLi[i]) } } function filter(li){for(var i=0; i<closeArr.length;i++){if(li == closeArr[i]){return false}}for(var i=0; i<openArr.length;i++){if(li == openArr[i]){return false}}return true; } for(var i=0; i< arr.length; i++){ if(Math.abs(nowLi.offsetLeft-arr[i].offsetLeft)<=(gridSize+1) && Math.abs(nowLi.offsetTop-arr[i].offsetTop)<=(gridSize+1)){ arr[i].num = f(arr[i]); arr[i].parent = nowLi; openArr.push(arr[i]) } } } function showLine(){var result = [];var lastLi = closeArr.pop();var iNow = 0;findParent(lastLi);function findParent(li){result.unshift(li);if( li.parent == beginLi[0] ){return;}findParent(li.parent);}var timer = setInterval(function(){result[iNow].style.background = 'red';iNow++;if(iNow == result.length){clearInterval(timer);}},500);} function f(nodeLi){ return g(nodeLi)+h(nodeLi) } function g(nodeLi){var a = beginLi[0].offsetLeft - nodeLi.offsetLeft;var b = beginLi[0].offsetTop - nodeLi.offsetTop;return Math.sqrt(a*a + b*b);}function h(nodeLi){var a = endLi[0].offsetLeft - nodeLi.offsetLeft;var b = endLi[0].offsetTop - nodeLi.offsetTop;return Math.sqrt(a*a + b*b);} } </script> </head> <body> <ul id="ul1"> </ul> <input type="button" id="input1" value="开始"/> </body></html>排列就不说，有快速排序法，二分法类的
快速排序
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8" /><title>无标题文档</title><script>var array=[13,3,5,6,7,3,7,8,2,4,1,4,4,5,6,7,88,99,9]//冒泡相当于先确定最大的。。。//而选择先确定开始最小的。//排序思想，将13与3比较，13大于3，换位置，变成[3,13,5,6,7,3,7,8,2,4,1,4,4,5,6,7,88,99,9]，再将13与5比较，大于，再J+1；function qSort(arr,low,high){ var i,j,x; if(low<high){ i=low; j=high; x=arr[i]; while(i<j){while( i<j && arr[j]>x){j--;} if(i<j){arr[i]=arr[j]i++;}while( i<j && arr[i]<x){i++;} if(i<j){arr[j]=arr[i]i--;}} } return arr}console.time('tt')alert(qSort(array,0,3));console.timeEnd('tt')</script></head><body></body></html><!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8" /><title>无标题文档</title><script>var array=[13,3,5,6,7,3,7,8,2,4,1,4,4,5,6,7,88,99,9]//冒泡相当于先确定最大的。。。//而选择先确定开始最小的。//排序思想，将13与3比较，13大于3，换位置，变成[3,13,5,6,7,3,7,8,2,4,1,4,4,5,6,7,88,99,9]，再将13与5比较，大于，再J+1；function bubbleSort(arr){for(var i=arr.length-1;i>0;i--){for(var j=0;j<i;j++){if(arr[j]>=arr[j+1]){var temp=0temp=arr[j+1];arr[j+1]=arr[j];arr[j]=temp;}console.log(i+'j:'+j) }} return arr}console.time('tt')alert(bubbleSort(array));console.timeEnd('tt')</script></head><body></body></html>二分法排序
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8" /><title>无标题文档</title><script>function quickSort(arr){if(arr.length<=1){return arr;}var num=Math.floor(arr.length/2);var numValue=arr.splice(num,1);var left=[];var right=[];for(var i=0;i<arr.length;i++){if(arr[i]<numValue){left.push(arr[i]);}else{right.push(arr[i]);}}return quickSort(left).concat([numValue],quickSort(right));}//quickSort([12,5,37,6,22,40])alert(quickSort([1,2,9,54,56,5,6,57,44,36]))</script></head><body></body></html> 0 0
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