Leetcode719.找出第k小的距离对二分 & 双指针

Posted 2021-10-07 nirvana · rebirth

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AC-Code

class Solution {
public:
    int smallestDistancePair(vector<int>& nums, int k) {
        sort(nums.begin(), nums.end());
        auto check = [&](int mid) -> bool { // 是否有至少k组，差值<=mid
            int cnt = 0, j = 1;
            for(int i = 0; i < nums.size(); ++i) {
                while(j < nums.size() && nums[j] - nums[i] <= mid) ++j;
                cnt += j - i - 1;
            }
            return cnt >= k;
        };
        int l = 0, r = nums[nums.size() - 1] - nums[0];
        while(l < r) {
            int mid = (l + r) >> 1;
            if(check(mid)) {
                r = mid;
            }
            else {
                l = mid + 1;
            }
        }
        return l;
    }
};