Force buckle 179, max

One 、 Title Description

Given a set of nonnegative integers nums, Rearrange the order of each number （ Each number cannot be split ） Make it the largest integer .
Be careful ： The output can be very large , So you need to return a string instead of an integer .

Two 、 Description of ideas

There is a skill to solve this problem , The sorting conditions are different from normal . When we sort an array , Just compare the two elements ( hypothesis x and y Is any two elements of the array ) The size is ok ：
as long as x > y, So if it is in descending order y It should be in x Behind
as long as x < y, So if it is in descending order x It should be in y Behind
For this subject , hypothesis x and y Is any two elements in the array , that x Yes, it needs to be y Is it in front of or behind ？ It depends on xy and yx Which is bigger and which is smaller ：
If xy > yx, that y Should be in x Behind
If xy < yx, that x Should be in y Behind
such as ,x = 30, y = 3, that xy = 303,yx = 330, because xy < yx , therefore 30 It should be in line 3 Behind , So we can get the maximum value

3、 ... and 、 Code

    //179、 The maximum number 
    public String largestNumber(int[] nums) {
    
        //  Sort 
        quickSort(nums,0,nums.length-1);
        if(nums[0]==0)
            return "0";
        StringBuilder sb = new StringBuilder();

        for(int num:nums){
    
            sb.append(num);
        }
        return sb.toString();
    }

    public void quickSort(int[] nums, int l, int h) {
    
        if (l >= h)
            return;
        int pivot = nums[h];
        int less = l;
        int great = h;
        int i = l;
        while (i <= great) {
    
            String xy = nums[i] + "" + pivot;
            String yx = pivot + "" + nums[i];
            if (xy.compareTo(yx) > 0) {
    
                swap(nums, i, less);
                less++;
                i++;
            } else if (xy.compareTo(yx) < 0) {
    
                swap(nums, i, great);
                great--;
            } else {
    
                i++;
            }

        }
        quickSort(nums,l,less-1);
        quickSort(nums,great+1,h);
    }


    public void swap(int[] nums, int i, int j) {
    
        int tmp = nums[i];
        nums[i] = nums[j];
        nums[j] = tmp;
    }