Tejav
#3524

Find X Value of Array I

Medium
ArrayMathDynamic ProgrammingHash MapArray
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Approaches

Brute ForceOptimal
Complexity Comparison
Brute ForceOptimal Solution★
Time
O(n²)
O(n)
Space
O(1)
O(k)
💡

Intuition

Time O(n)Space O(k)

We can use dynamic programming to keep track of products modulo k as we iterate through the array, counting occurrences efficiently.

⚙️

Algorithm

3 steps
  1. 1Step 1: Initialize a dp array to count occurrences of each remainder.
  2. 2Step 2: Iterate through the array, updating the product and its remainder.
  3. 3Step 3: Use the dp array to accumulate counts for each remainder.
solution.py10 lines
1def countWays(nums, k):
2    result = [0] * k
3    dp = [0] * k
4    product = 1
5    for num in nums:
6        product = (product * num) % k
7        dp[product] += 1
8    for r in range(k):
9        result[r] = dp[r]
10    return result
ℹ

Complexity note: This complexity is linear due to a single pass through the array and constant time updates to the dp array.

  • 1Dynamic programming helps reduce redundant calculations.
  • 2Tracking remainders allows efficient counting.

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