[Leetcode] #164 Maximum Gap

最新推荐文章于 2021-02-26 15:12:35 发布

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最新推荐文章于 2021-02-26 15:12:35 发布

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分类专栏： LeetCode

本文链接：https://blog.youkuaiyun.com/qq_34264472/article/details/77921864

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本文介绍了一种线性时间和空间复杂度的算法，用于找到未排序数组中排序后相邻元素的最大间隔。该算法首先确定数组中的最小和最大值，然后通过桶排序的方式计算最大间隔。

Discription

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

int maximumGap(vector<int> &num) {
	if (num.size() < 2)
		return 0;
	int size = num.size();
	int Min = num[0];
	int Max = num[0];
	for (int i = 1; i < size; ++i){
		Max = max(Max, num[i]);
		Min = min(Min, num[i]);
	}
	int gap = (Max - Min) / (size - 1) + 1;
	int bucketNum = (Max - Min) / gap + 1;
	vector<int> bucketsMin(bucketNum, INT_MAX);
	vector<int> bucketsMax(bucketNum, INT_MIN);
	for (int i = 0; i < size; ++i){
		if (num[i] == Max || num[i] == Min)
			continue;
		int index = (num[i] - Min) / gap;
		bucketsMin[index] = min(bucketsMin[index], num[i]);
		bucketsMax[index] = max(bucketsMax[index], num[i]);
	}
	int maxGap = 0;
	int pre = Min;
	for (int i = 0; i < bucketNum; ++i){
		if (bucketsMin[i] == INT_MAX || bucketsMax[i] == INT_MIN)
			continue;
		maxGap = max(maxGap, bucketsMin[i] - pre);
		pre = bucketsMax[i];
	}
	maxGap = max(maxGap, Max - pre);
	return maxGap;
}

GitHub-Leetcode: https://github.com/wenwu313/LeetCode