leetcode-Array篇easy难度之求指定偏移量元素数量

关键词

绝对值，二分查找，上下界，TreeSet

题目描述

https://leetcode.com/problems/find-the-distance-value-between-two-arrays/

Given two integer arrays arr1 and arr2, and the integer d, return the distance
 value between the two arrays.

The distance value is defined as the number of elements arr1[i] such that 

there is not any element arr2[j] where |arr1[i]-arr2[j]| <= d.

 

Example 1:

Input: arr1 = [4,5,8], arr2 = [10,9,1,8], d = 2
Output: 2
Explanation: 
For arr1[0]=4 we have: 
|4-10|=6 > d=2 
|4-9|=5 > d=2 
|4-1|=3 > d=2 
|4-8|=4 > d=2 
For arr1[1]=5 we have: 
|5-10|=5 > d=2 
|5-9|=4 > d=2 
|5-1|=4 > d=2 
|5-8|=3 > d=2
For arr1[2]=8 we have:
|8-10|=2 <= d=2
|8-9|=1 <= d=2
|8-1|=7 > d=2
|8-8|=0 <= d=2
Example 2:

Input: arr1 = [1,4,2,3], arr2 = [-4,-3,6,10,20,30], d = 3
Output: 2
Example 3:

Input: arr1 = [2,1,100,3], arr2 = [-5,-2,10,-3,7], d = 6
Output: 1

博主第一次提交的代码

查边界的地方代码还能优化，并且排序的这个方式感觉有点多余

class Solution {
    public int findTheDistanceValue(int[] arr1, int[] arr2, int d) {
        int min = Integer.MAX_VALUE;
        int max = Integer.MIN_VALUE;
        int[] arr2Clone = arr2.clone();
        Arrays.sort(arr2Clone);
        for(int eachArr2: arr2){
            if( eachArr2 < min){
                min = eachArr2;
            }
            if( eachArr2 > max){
                max = eachArr2;
            }
        }
        int result  = 0;
        for(int eachArr1: arr1){
            if( (eachArr1  - max > d  ) || (min - eachArr1 > d ) ) {
                result++;
            }
            for(int i = 0 ; i < arr2Clone.length - 1; i++){
                if( (eachArr1 - arr2Clone[i]) > d &&  (arr2Clone[i+1] - eachArr1) > d   ){
                    result++;
                }
            }
        }
        return result;
        
    }
    
    
    
}

其他人优秀的代码

https://leetcode.com/problems/find-the-distance-value-between-two-arrays/discuss/546441/Simple-Java-solution-using-TreeSet

class Solution {
    public int findTheDistanceValue(int[] arr1, int[] arr2, int d) {
        int res = 0;
        TreeSet ts = new TreeSet<>();
        for(int n : arr2)
            ts.add(n);
        
        for(int n : arr1){
            Integer higher = ts.ceiling(n);
            Integer lower = ts.floor(n);
            int diff = 0;
            if(higher == null){
                diff = Math.abs(lower - n);
            }else if(lower == null){
                diff = Math.abs(higher - n);
            }else{
                diff = Math.min(higher - n, n - lower);
            }
            if(diff > d)
                res++;
        }
        return res;
    }
}