力扣：719. 找出第 K 小的数对距离

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;


public class Solution {
    public static void main(String[] args) {
        Solution solution = new Solution();
        int[] nums = {1,3,1};
        System.out.println(solution.smallestDistancePair(nums, 1));
    }

    public int smallestDistancePair(int[] nums, int k) {
        Arrays.sort(nums);
        int n = nums.length, left = 0, right = nums[n - 1] - nums[0];
        while (left <= right){
            int mid = (left + right) >> 1;
            int cnt = 0;

            for (int i = 1; i < n; i++){
                cnt += i - binarySearch(nums, i, nums[i] - mid);
            }

            if (cnt >= k){
                right = mid -1;
            } else {
                left = mid + 1;
            }
        }
        return left;
    }

    private int binarySearch(int[] nums, int end, int target){
        int left = 0, right = end;
        while (left <= right){
            int mid = (left + right) >> 1;
            if (nums[mid] >= target ){
                right = mid - 1;
            } else {
                left = mid + 1;
            }
        }
        return left;
    }

}