冒泡排序和二分查找

<script type="text/javascript">

    /**

     * js 冒泡排序

     */

    //var  numArr = [-3,-10,0,32,9,3,23];

    var  numArr = [-1,0,3,23,34,];

    var flag = false;

    for(var i = 0; i < numArr.length -1; i++) { //控制比较多少轮

        document.writeln("比较多少轮：" + (i+1) + "<br />");

        for(var j = 0; j < numArr.length - i -1;j++) {//控制每轮比较的次数

            if(numArr[j] > numArr[j+1]) {

                //交换 //从小到大

                var temp = numArr[j];

                numArr[j] = numArr[j+1];

                numArr[j+1] = temp;

                flag = true;

            }

//if(numArr[j] < numArr[j+1]) { //从大到小 // //交换 // var temp = numArr[j+1]; //numArr[j+1] = numArr[j]; //numArr[j] = temp; //flag = true;

 

        }

        if(flag) {

            flag = false;

        } else {

            //禁止循环，这样做的好处：当数组有序时就不要在循环了

            break;

        }

                             

    }

    document.writeln(numArr);

</script>

 

 

<script type="text/javascript">

    /**

     * JS的二分查找

     * 1.注意事项：二分查找必须针对的是有序的数组，不是有序的数组不能使用二分查找法

     * 2.思路：首先找到数组的中间数(midVal),和你要查找的数(findVal)进行比较，如果

     * midVal > findVal ,则说明在数组的左边，就把该数组二分（就只在左边查找）

     */

                

    function binarySearch(arr,findVal,leftIndex,rightIndex) {

        //防止无穷递归

        if(leftIndex > rightIndex) {

            document.writeln("找不到");

            return;

        }

        //找到中间这个值

        var midIndex = Math.floor((leftIndex + rightIndex)/2);

        var midVal = arr[midIndex];

        //比较

        if(midVal > findVal) {

            //在左边查找

            binarySearch(arr,findVal,leftIndex,midIndex - 1);

        } else if(midVal < findVal) {

            //在右边查找

            binarySearch(arr,findVal,midIndex+1,rightIndex);

        } else {

            document.writeln("找到了，位置为：" + midIndex);

            return;

        }

    }

    var arr = [1,2,5,67,89,90];

    binarySearch(arr,3,0,arr.length -1);

</script>

 

<script type="text/javascript">

    /*数组的简单行列倒置*/

    var arr = [[2,4,6,8],[1,3,5,9],[9,7,4,2]];

            

    //定义一个新的数组

    var arr2 = [];

    //初始化新数组的行数,我认为该数组是规则的,并初始化

    for(var i = 0; i < arr[0].length; i++) {

        arr2[i] = [];

    }

            

    //动态的添加新数据，遍历旧数据

    for(var i=0; i < arr.length; i++) {

        for(var j=0; j < arr[i].length; j++) {

            arr2[j][i] = arr[i][j];

        }

    }

            

    //遍历新数组，显示数据

    for(var i=0; i < arr2.length; i++) {

        for(var j=0; j < arr2[i].length; j++) {

            document.writeln(arr2[i][j] + " ");

        }

        document.writeln("<br />");

    }

            

</script>

http://hanchaohan.blog.51cto.com/2996417/1308498