js 乱序数组

第一种时间复杂度O(n^2)

var arr = [0,1,2,3,4,5,6];

var len = arr.length;
for(var i=0;i<len;i++) {
    var index = Math.floor(Math.random()*(len-i));
    var tem = arr[index];
    arr[index] = arr[len-i-1];
    arr[len-i-1] = tem;
}

console.log(arr);

第二种方法时间复杂度O(n)

var arr = [0,1,2,3,4,5,6];
function f2(arr1) {
    var arr2 = [];
    while(arr1.length>0){
        var index = Math.floor(Math.random()*arr1.length);
        arr2.push(arr1[index]);
        arr1.splice(index,1);
    }
    return arr2;
}

console.log(f2(arr));