164. 最大间距

链接：164. 最大间距

题解：https://leetcode-cn.com/problems/maximum-gap/solution/zui-da-jian-ju-by-leetcode-solution/

class Solution {
public:
    int maximumGap(vector<int>& nums) {
        int n = nums.size();
        if (n < 2) {
            return 0;
        }
        int minVal = *min_element(nums.begin(), nums.end());
        int maxVal = *max_element(nums.begin(), nums.end());
        int d = max(1, (maxVal - minVal) / (n - 1)); // 两个桶之间的间隙
        int bucketSize = (maxVal - minVal) / d + 1; // 桶的个数

        vector<pair<int, int>> bucket(bucketSize, {-1, -1});  // 存储 (桶内最小值，桶内最大值) 对，(-1, -1) 表示该桶是空的
        for (int i = 0; i < n; i++) {
            // 需要放入桶的下标
            int idx = (nums[i] - minVal) / d;
            // 桶之前没有元素
            if (bucket[idx].first == -1) {
                bucket[idx].first = bucket[idx].second = nums[i];
            } else {
                bucket[idx].first = min(bucket[idx].first, nums[i]);
                bucket[idx].second = max(bucket[idx].second, nums[i]);
            }
        }

        int ret = 0;
        int prev = -1;
        // 比较相邻两个有值的桶
        for (int i = 0; i < bucketSize; i++) {
            if (bucket[i].first == -1) continue;
            if (prev != -1) {
                ret = max(ret, bucket[i].first - bucket[prev].second);
            }
            prev = i;
        }
        return ret;
    }
};