Maximum Gap

Maximum Gap

问题：

Given an unsorted array, find the maximum difference between the successive elements in its sorted form.

Try to solve it in linear time/space.

Return 0 if the array contains less than 2 elements.

You may assume all elements in the array are non-negative integers and fit in the 32-bit signed integer range.

思路：

　　基数排序的应用

我的代码：

public class Solution {

    public int maximumGap(int[] nums) {

        if(nums==null || nums.length<2) return 0;

        radixSort(nums, 2, 32);

        int diff = Integer.MIN_VALUE;

        

        for(int i=1; i<nums.length; i++)

        {

            diff = Math.max(diff, nums[i]-nums[i-1]);

        }

        return diff;

    }

    private void radixSort(int[] nums,int radix, int distance) {  

        int length = nums.length;  

        int[] temp = new int[length];//用于暂存元素  

        int[] count = new int[radix];//用于计数排序  

        int divide = 1;  

        for (int i = 0; i < distance; i++) {  

            System.arraycopy(nums, 0,temp, 0, length);  

            Arrays.fill(count, 0);  

              

            for(int j=0; j<length; j++)

            {

                int tmpKey = (temp[j]/divide%radix);

                count[tmpKey]++;

            }

            for(int j=1; j<radix; j++)

            {

                count[j] = count[j]+count[j-1];

            }

            

            for(int j=length-1; j>=0; j--)

            {

                int tmpKey = (temp[j]/divide%radix);

                count[tmpKey]--;

                nums[count[tmpKey]] = temp[j];

            }

              

            divide = divide * radix;                  

        }  

                  

    }  

}

View Code

学习之处：

• 基数排序最后一步要从后往前来，因为后面的比前面的大，最佳反例 2，33比较到第二位还是2,33 但是当比较到第三位就是 33,2了，画画就明白了