LeetCode Entry

3228. Maximum Number of Operations to Move Ones to the End

13.11.2025 medium 2025 kotlin rust

Max steps to move all ones to the right

3228. Maximum Number of Operations to Move Ones to the End medium blog post substack youtube

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Problem TLDR

Max steps to move all ones to the right #medium

Intuition

    // 1010101010
    // 1010101001
    // 1010100011
    // 1010000111
    // 1000001111
    // 0000011111
    //
    //  a b c d e
    // 1010101010
    // 0110101010 a-1
    // 0101101010 b-1
    // 0011101010 b-2
    // 0011011010 c-1
    // 0010111010 c-2
    // 0001111010 c-3
    // 0001110110 d-1
    // 0001101110 d-2
    // 0001011110 d-3
    // 0000111110 d-5
    // 0000111110 e-5 bubble '0' to the left
    // go from left to right, each zero gives +(number of ones)
    // dedup zeros

Go from left to right and count ones; each zero adds +count_ones

Approach

• skip duplicate consequent zeros

Complexity

• Time complexity: \(O(n)\)

• Space complexity: \(O(1)\)

Code

// 39ms
fun maxOperations(s: String) = s.indices.fold(0 to 0) {(o,r),i->
    o+(s[i]-'0') to if (s[i]>'0'||i>0 && s[i]==s[i-1]) r else r+o}.second

// 0ms
    pub fn max_operations(s: String) -> i32 {
        let (mut o, s) = (0, s.as_bytes());
        (0..s.len()).map(|i| { o += (s[i] - b'0') as i32;
            if i>0&&s[i]==s[i-1]||s[i]==b'1'{0}else{o}
        }).sum()
    }