LeetCode Entry

2169. Count Operations to Obtain Zero

09.11.2025 easy 2025 kotlin rust

Count numbers subtractions until 0

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Problem TLDR

Count numbers subtractions until 0 #easy

Intuition

Simulate the process.

Another way to look at it: the biggest would be subtracted big/small times until numbers flip.

Approach

• recursion space complexity is log(depth)
• it is Euclidian algorithm (a,b) to (b, a%b)
• there is a golden ratio hidden here
• consequtive Fibonacci numbers would give the slowest path: Fibonacci sequence backwards

Complexity

• Time complexity: \(O(log(n))\)

• Space complexity: \(O(log(n))\)

Code

// 0ms
    fun countOperations(a: Int, b: Int): Int =
        if (a<1||b<1) 0 else a/b + countOperations(b,a%b)

// 0ms
    pub fn count_operations(a: i32, b: i32) -> i32 {
        if a<1 || b<1 { 0 } else { a/b + Self::count_operations(b,a%b) }
    }