LeetCode Entry

1018. Binary Prefix Divisible By 5

24.11.2025 easy 2025 kotlin rust

Prefixes divisible by 5

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Problem TLDR

Prefixes divisible by 5 #easy #brainteaser

Intuition

    // its not easy; its brainteaser
    // the 10^5 length
    // how to convert base_2 to base_5 directly?
    // to convert to base_10
    // let's try convert to long base_10
    // it goes out of range too fast
    // can we trim it % 5?

Approach

• the remainder of %5 is enough

Complexity

• Time complexity: \(O(n)\)

• Space complexity: \(O(1)\)

Code

// 3ms
    fun prefixesDivBy5(n: IntArray) =
    { var x = 0; n.map {x = (x*2+it)%5; x<1 }}()

// 0ms
    pub fn prefixes_div_by5(n: Vec<i32>) -> Vec<bool> {
        let mut x = 0; n.iter().map(|&n|{x=(x*2+n)%5; x<1}).collect()
    }