LeetCode-Maximum Gap

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.

Solution:

public class Solution {
    public int maximumGap(int[] num) {
        int len = num.length;
        if (len<2) return 0;
        if (len==2) return num[1]-num[0];

        int numMax = num[0], numMin = num[0];
        for (int i:num){
            numMax = Math.max(numMax,i);
            numMin = Math.min(numMin,i);
        }
        double temp = (double) numMax - numMin;
            int gap = (int) Math.ceil(temp/(len-1));

        int[] bucketMin = new int[len-1];
        int[] bucketMax = new int[len-1];
        Arrays.fill(bucketMin, Integer.MAX_VALUE);
        Arrays.fill(bucketMax, Integer.MIN_VALUE);
        for (int i:num){
            int index = (i-numMin)/gap;
            if (i==numMax) index = len-2;
            if (i>bucketMax[index]) bucketMax[index] = i;
            if (i<bucketMin[index]) bucketMin[index] = i;
        }

        int res = Integer.MIN_VALUE;
        int pre = bucketMax[0];
        for (int i=1;i<len-1;i++)
            if (bucketMin[i] == Integer.MAX_VALUE) continue;
            else {
                if (res<(bucketMin[i]-pre))
                    res = bucketMin[i]-pre;
                pre = bucketMax[i];
            }
        
        return res;
    }
}