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// @Title: 差的绝对值为 K 的数对数目 (Count Number of Pairs With Absolute Difference K)
// @Author: 15816537946@163.com
// @Date: 2022-02-09 23:34:14
// @Runtime: 0 ms
// @Memory: 2.1 MB
use std::collections::HashMap;
// struct Solution;
impl Solution {
    pub fn count_k_difference(nums: Vec<i32>, k: i32) -> i32 {
        nums.iter()
            .enumerate()
            .map(|(ind, &x)| {
                nums[ind + 1..]
                    .iter()
                    .filter(|&&y| (x - y).abs() == k)
                    .count() as i32
            })
            .sum::<_>()
    }
}