leetcode 155: Maximum Gap

最新推荐文章于 2017-01-21 13:58:14 发布

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本文介绍了一种在不排序数组的情况下找到数组中相邻元素最大差距的方法，通过使用线性时间复杂度和常数空间复杂度实现。适用于非负整数数组且数值范围在32位有符号整数范围内。

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Maximum Gap

Total Accepted: 2946 Total Submissions: 12695

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.

public class Solution {
    public int maximumGap(int[] num) {
           if(num == null || num.length < 2) return 0;
        
        int min = num[0], max = num[0];
        int len = num.length;
        for(int i=1; i<len; i++) {
            if(num[i] < min) {
                min = num[i];
            } else if(num[i] > max) {
                max = num[i];
            }
        }
        if(len==2) return max - min;
        int [] min_bs = new int[len+1];
        int [] max_bs = new int[len+1];
        
        for(int i=0; i<len; i++) {
            int x = num[i];
            int k =  (int)(len * (1.0 * (x - min) / (max - min))); //attention! may have overflow problem!
            if(min_bs[k]==0 || x<min_bs[k]) min_bs[k] = x;
            if(max_bs[k]==0 || x>max_bs[k]) max_bs[k] = x;
        }
        
        int maxInter = 0;
        min = max_bs[0];
        for(int i=1; i<len+1; i++) {
            if(min_bs[i] == 0) continue;
            maxInter = Math.max(maxInter, min_bs[i] - min);
            min = max_bs[i];
        }
        return maxInter;
        
    }
}