164. 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.

class Solution {
    public int maximumGap(int[] nums) {
        if (nums.length<2) return 0;
        int minNum = -1, maxNum = -1, n = nums.length;
        for (int i=0; i<n; ++i) {
            minNum = min(nums[i], minNum);
            maxNum = max(nums[i], maxNum);
        }
        if (maxNum==minNum) return 0;
        double average = (maxNum-minNum) * 1.0 / (n - 1);
        if (average==0) ++average;
        int[] localMin = new int[n];
        int[] localMax = new int[n];
        for (int i=0; i<n; ++i) {
            localMin[i] = -1;
            localMax[i] = -1;
        }
        for (int i=0; i<n; ++i) {
            int t = (int)((nums[i]-minNum) / average);
            localMin[t] = min(localMin[t], nums[i]);
            localMax[t] = max(localMax[t], nums[i]);
        }
        int ans = (int)average, left = 0, right = 1;
        while (left<n-1) {
            while (right<n && localMin[right]==-1) ++right;
            if (right>=n) break;
            ans = max(ans, localMin[right]-localMax[left]);
            left = right;
            ++right;
        }
        return ans;
    }
    
    private int min(int a, int b) {
        if (a==-1) return b;
        else 
            if (b==-1) return a;
            else
                if (a<b) return a;
                else return b;
    }
    
    private int max(int a, int b) {
        if (a==-1) return b;
        else
            if (b==-1) return a;
            else
                if (a>b) return a;
                else return b;    
    }
}

/**
 * @param {number[]} nums
 * @return {number}
 */
var maximumGap = function(nums) {
    var k = maxDigit(nums);
    for(var i = 0; i < k; i++){
        var arr = Array.from({length: 10}, () => []);
        for(var j = 0; j < nums.length; j++){
            var digit = getDigit(nums[j], i);
            arr[digit].push(nums[j]);
        }
        nums = [].concat(...arr)
    }
    var range = 0;
    for(var j = 1; j < nums.length; j++){
        range = Math.max(range, nums[j] - nums[j - 1]);
    }    
    return range;
}
function getDigit(nums, i){
    return Math.floor(nums / Math.pow(10, i) % 10);
}
function digitCount(nums){
    if(nums === 0) return 1;
    return Math.floor(Math.log10(nums)) + 1;
}
function maxDigit(nums){
    var max = 0;
    for(var i = 0; i < nums.length; i++){
        max = Math.max(max, digitCount(nums[i]));
    }
    return max;
}