LeetCode

Maximum Gap

2015.1.23 15:00

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:

　　This here is not an O(n) solution, but O(n * log(n)). Sort the array and find the maximal gap.

　　As for a linear solution, I'm searching for it...

　　Discussions online said it could be solved using bucket sort, but that doesn't really satisfy O(n) time scale, right? At least I wouldn't take it for O(n).

Accepted code:

// 1AC, not an O(n) solution, though, one not yet come up with...
#include <algorithm>
using namespace std;

class Solution {
public:
    int maximumGap(vector<int> &num) {
        sort(num.begin(), num.end());
        int n;
        
        n = (int)num.size();
        if (n < 2) {
            return 0;
        }
        
        int i;
        int ans = abs(num[0] - num[1]);
        for (i = 2; i < n; ++i) {
            ans = max(ans, abs(num[i - 1] - num[i]));
        }
        
        return ans;
    }
private:
    int max(const int &x, const int &y) {
        return x > y ? x : y;
    }
    
    int abs(const int &x) {
        return x >= 0 ? x : -x;
    }
};