leetcode 164. Maximum Gap

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.

要求线性时间，只能空间换时间，用计数排序，出现过的num用map来存。
   并且在map里面会自动排序，小的在前。

class Solution {public:    int maximumGap(vector<int>& nums)     {        if (nums.size() < 2)            return 0;                   map<int,int> pp;        for (int i = 0; i < nums.size(); i++)            pp[nums[i]]++;                     int ret = 0;            int lastnum = -1;        for(auto it = pp.begin(); it != pp.end(); it++)        {            if (lastnum != -1)                ret = max(ret , (it->first - lastnum) );            lastnum = it->first;        }        return ret;    }};