/**
 * [67] Add Binary
 */
pub struct Solution {}


// submission codes start here

impl Solution {
    pub fn add_binary(a: String, b: String) -> String {
        let a: Vec<u32> = a.chars().rev().map(|c| c.to_digit(10).unwrap()).collect();
        let b: Vec<u32> = b.chars().rev().map(|c| c.to_digit(10).unwrap()).collect();

        let mut result: Vec<u32> = Vec::with_capacity(a.len().max(b.len()) + 2);

        let mut overflow = 0;
        for i in 0..a.len().max(b.len()) {
            let mut bit = overflow;
            
            if i < a.len() {
                bit += a[i];
            }
            if i < b.len() {
                bit += b[i];
            }
            
            match bit { 
                3 => {result.push(1); overflow = 1},
                2 => {result.push(0); overflow = 1},
                1 => {result.push(1); overflow = 0},
                0 => {result.push(0); overflow = 0},
                _ => {}
            }
        }
        
        if overflow != 0 {
            result.push(overflow);
        }
        
        if result.len() == 0 {
            result.push(0);
        }

        result.iter().rev().map(|i| i.to_string()).collect()
    }
}

// submission codes end

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_67() {
        assert_eq!("100".to_owned(), Solution::add_binary("11".to_owned(), "1".to_owned()));
        assert_eq!("10101".to_owned(), Solution::add_binary("1010".to_owned(), "1011".to_owned()));
        assert_eq!("110110".to_owned(), Solution::add_binary("100".to_owned(), "110010".to_owned()));
    }
}