[leetcode]Maximum Gap

バケツを分ける方法で、考え方はネットユーザーから参考にして、とてもすばらしいです.

class Solution {

public:

    int maximumGap(vector<int> &num) {

        int size = num.size();

        if (size < 2) {

            return 0;

        }

        int maxVal = *max_element(num.begin(), num.end());

        int minVal = *min_element(num.begin(), num.end());

        int gap = (maxVal - minVal - 1) / (size - 1) + 1; // ceiling function

        int bucketSize = (maxVal - minVal) / gap;

        vector<int> minBucket(bucketSize, INT_MAX);

        vector<int> maxBucket(bucketSize, INT_MIN);

        for (int i = 0; i < size; i++) {

            if (num[i] == minVal || num[i] == maxVal) {

                continue;

            }

            int idx = (num[i] - minVal) / gap;

            minBucket[idx] = min(minBucket[idx], num[i]);

            maxBucket[idx] = max(maxBucket[idx], num[i]);

        }

        int maxGap = INT_MIN;

        int prev = minVal;

        for (int i = 0; i < bucketSize; i++) {

            if (minBucket[i] != INT_MAX) {

                maxGap = max(maxGap, minBucket[i] - prev);

                prev = maxBucket[i];

            }

        }

        maxGap = max(maxGap, maxVal - prev);

        return maxGap;

    }

};