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

problem

You are given a binary string s.

You can perform the following operation on the string any number of times:

• Choose any index i from the string where i + 1 < s.length such that s[i] == '1' and s[i + 1] == '0'.
• Move the character s[i] to the right until it reaches the end of the string or another '1'. For example, for s = "010010", if we choose i = 1, the resulting string will be s = "000110".

Return the maximum number of operations that you can perform.

Example 1:

Example 2:

Constraints:

• 1 <= s.length <= 105
• s[i] is either '0' or '1'.

submission

// the optimal strategy for this problem is just move '1's
// starting from left to right, this way, we can 'split'
// the movement of '1's into as many parts as possible.
// we calculate the #operations by iteration and counting
impl Solution {
    pub fn max_operations(s: String) -> i32 {
        s.as_bytes()
            .windows(2)
            .scan(0, |acc, win| match win {
                &[b'1', b'0'] => {
                    // encountered a split, yield acc
                    // also raise acc
                    *acc += 1;
                    Some(*acc)
                }
                &[b'1', _] => {
                    // encountered a '1' but not a split
                    // raise acc yield 0
                    *acc += 1;
                    Some(0)
                }
                _ => Some(0),
            })
            .sum()
    }
}