LeetCode 164 Maximum Gap (C++, Python)

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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 C++


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class Solution {
    void radixSort(vector<int>&num, int exp) {
        vector<int>output(num.size(), 0);
        int count[10] = {0};
        for (int n: num) {
            count[n / exp % 10] ++;
        }

        for (int i = 1; i < 10; ++i) {
            count[i] += count[i - 1];
        }
        for (auto it = num.rbegin(); it != num.rend(); ++it) {
            output[count[*it / exp % 10] - 1] = *it;
            count[*it / exp % 10] --;
        }
        num = output;
    }
public:
    int maximumGap(vector<int> &num) {
        int diff = 0;
        if (num.size() < 2) return diff;
        int upper = *max_element(num.begin(), num.end());
        for (int exp = 1; upper / exp > 0; exp *= 10) {
            radixSort(num, exp);
        }

        for (int i = 1; i < num.size(); ++i) {
            diff = max(diff, num[i] - num[i - 1]);
        }
        return diff;
    }
};
Solution Python


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class Solution:
    def radixSort(self, num):
        upper = max(num)
        exp = 1
        while True:
            if upper / exp == 0: break
            self.counterSort(num, exp)
            exp *= 10
            
    def counterSort(self, num, exp):
        output = [0] * len(num)
        counter = [0] * 10
        for n in num:
            counter[n / exp % 10] += 1
        for i in range(1, 10):
            counter[i] += counter[i - 1]
        for i in range(len(num) - 1, -1, -1):
            output[counter[num[i] / exp % 10] - 1] = num[i]
            counter[num[i] / exp % 10] -= 1
        num[:] = output
        
    # @param num, a list of integer
    # @return an integer
    def maximumGap(self, num):
        diff = 0;
        if len(num) < 2: return diff
        self.radixSort(num)
        for i in range(1, len(num)):
            diff = max(diff, num[i] - num[i - 1])
        return diff

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