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2670. Find the Distinct Difference Array

Description

You are given a 0-indexed array nums of length n.

The distinct difference array of nums is an array diff of length n such that diff[i] is equal to the number of distinct elements in the suffix nums[i + 1, ..., n - 1] subtracted from the number of distinct elements in the prefix nums[0, ..., i].

Return the distinct difference array of nums.

Note that nums[i, ..., j] denotes the subarray of nums starting at index i and ending at index j inclusive. Particularly, if i > j then nums[i, ..., j] denotes an empty subarray.

 

Example 1:

Input: nums = [1,2,3,4,5]
Output: [-3,-1,1,3,5]
Explanation: For index i = 0, there is 1 element in the prefix and 4 distinct elements in the suffix. Thus, diff[0] = 1 - 4 = -3.
For index i = 1, there are 2 distinct elements in the prefix and 3 distinct elements in the suffix. Thus, diff[1] = 2 - 3 = -1.
For index i = 2, there are 3 distinct elements in the prefix and 2 distinct elements in the suffix. Thus, diff[2] = 3 - 2 = 1.
For index i = 3, there are 4 distinct elements in the prefix and 1 distinct element in the suffix. Thus, diff[3] = 4 - 1 = 3.
For index i = 4, there are 5 distinct elements in the prefix and no elements in the suffix. Thus, diff[4] = 5 - 0 = 5.

Example 2:

Input: nums = [3,2,3,4,2]
Output: [-2,-1,0,2,3]
Explanation: For index i = 0, there is 1 element in the prefix and 3 distinct elements in the suffix. Thus, diff[0] = 1 - 3 = -2.
For index i = 1, there are 2 distinct elements in the prefix and 3 distinct elements in the suffix. Thus, diff[1] = 2 - 3 = -1.
For index i = 2, there are 2 distinct elements in the prefix and 2 distinct elements in the suffix. Thus, diff[2] = 2 - 2 = 0.
For index i = 3, there are 3 distinct elements in the prefix and 1 distinct element in the suffix. Thus, diff[3] = 3 - 1 = 2.
For index i = 4, there are 3 distinct elements in the prefix and no elements in the suffix. Thus, diff[4] = 3 - 0 = 3.

 

Constraints:

  • 1 <= n == nums.length <= 50
  • 1 <= nums[i] <= 50

Solutions

  • class Solution {
    public int[] distinctDifferenceArray(int[] nums) {
        int n = nums.length;
        int[] suf = new int[n + 1];
        Set<Integer> s = new HashSet<>();
        for (int i = n - 1; i >= 0; --i) {
            s.add(nums[i]);
            suf[i] = s.size();
        }
        s.clear();
        int[] ans = new int[n];
        for (int i = 0; i < n; ++i) {
            s.add(nums[i]);
            ans[i] = s.size() - suf[i + 1];
        }
        return ans;
    }
}

  • class Solution {
public:
    vector<int> distinctDifferenceArray(vector<int>& nums) {
        int n = nums.size();
        vector<int> suf(n + 1);
        unordered_set<int> s;
        for (int i = n - 1; i >= 0; --i) {
            s.insert(nums[i]);
            suf[i] = s.size();
        }
        s.clear();
        vector<int> ans(n);
        for (int i = 0; i < n; ++i) {
            s.insert(nums[i]);
            ans[i] = s.size() - suf[i + 1];
        }
        return ans;
    }
};

  • class Solution:
    def distinctDifferenceArray(self, nums: List[int]) -> List[int]:
        n = len(nums)
        suf = [0] * (n + 1)
        s = set()
        for i in range(n - 1, -1, -1):
            s.add(nums[i])
            suf[i] = len(s)

        s.clear()
        ans = [0] * n
        for i, x in enumerate(nums):
            s.add(x)
            ans[i] = len(s) - suf[i + 1]
        return ans


  • func distinctDifferenceArray(nums []int) []int {
	n := len(nums)
	suf := make([]int, n+1)
	s := map[int]bool{}
	for i := n - 1; i >= 0; i-- {
		s[nums[i]] = true
		suf[i] = len(s)
	}
	ans := make([]int, n)
	s = map[int]bool{}
	for i, x := range nums {
		s[x] = true
		ans[i] = len(s) - suf[i+1]
	}
	return ans
}

  • function distinctDifferenceArray(nums: number[]): number[] {
    const n = nums.length;
    const suf: number[] = new Array(n + 1).fill(0);
    const s: Set<number> = new Set();
    for (let i = n - 1; i >= 0; --i) {
        s.add(nums[i]);
        suf[i] = s.size;
    }
    s.clear();
    const ans: number[] = new Array(n);
    for (let i = 0; i < n; ++i) {
        s.add(nums[i]);
        ans[i] = s.size - suf[i + 1];
    }
    return ans;
}


  • use std::collections::HashSet;

impl Solution {
    pub fn distinct_difference_array(nums: Vec<i32>) -> Vec<i32> {
        let n = nums.len();
        let mut s = vec![0; n + 1];
        let mut set = HashSet::new();

        for i in (0..n).rev() {
            set.insert(nums[i]);
            s[i] = set.len();
        }

        let mut ans = Vec::new();
        set.clear();
        for i in 0..n {
            set.insert(nums[i]);
            ans.push((set.len() - s[i + 1]) as i32);
        }

        ans
    }
}

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