hashmap 1726

1726. Tuple with Same Product Medium 47322Add to ListShare

Given an array nums of distinct positive integers, return the number of tuples (a, b, c, d) such that a * b = c * d where a, b, c, and d are elements of nums, and a != b != c != d.

 Example 1:

Input: nums = [2,3,4,6]
Output: 8
Explanation: There are 8 valid tuples:
(2,6,3,4) , (2,6,4,3) , (6,2,3,4) , (6,2,4,3)
(3,4,2,6) , (4,3,2,6) , (3,4,6,2) , (4,3,6,2)

Example 2:

Input: nums = [1,2,4,5,10]
Output: 16
Explanation: There are 16 valid tuples:
(1,10,2,5) , (1,10,5,2) , (10,1,2,5) , (10,1,5,2)
(2,5,1,10) , (2,5,10,1) , (5,2,1,10) , (5,2,10,1)
(2,10,4,5) , (2,10,5,4) , (10,2,4,5) , (10,2,5,4)
(4,5,2,10) , (4,5,10,2) , (5,4,2,10) , (5,4,10,2)

Constraints:

• 1 <= nums.length <= 1000
• 1 <= nums[i] <= 104
• All elements in nums are distinct.

class Solution {
    public int tupleSameProduct(int[] nums) {
        HashMap<Integer,Integer> map = new HashMap();
        for(int i=0;i<nums.length-1;i++){
            for(int j=i+1;j<nums.length;j++){
                int sum = nums[i]*nums[j];
                map.put(sum, map.getOrDefault(sum,0)+1);
            }
        }
        int result = 0;
        for(int key:map.keySet()){
            result += count(map.get(key));
        }
        return result;
    }
    private int count(int num){
        if(num<2) return 0;
        if(num==2) return 8;
        return count(num-1)+8*(num-1);
    }
}

 

标签：10,hashmap,nums,1726,There,int,tuples,Output
来源： https://www.cnblogs.com/cynrjy/p/16683315.html