1
Fork 0
leetcode/source/add_binary/mod.rs

62 lines
1.5 KiB
Rust
Raw Normal View History

2022-04-07 22:06:19 +00:00
pub fn add_binary(a: String, b: String) -> String {
// Pad the strings with leading zeroes so they're the same length.
let (a, b) = (
format!("{:0>1$}", a, b.len()),
format!("{:0>1$}", b, a.len()),
);
let mut carry = false;
let mut sum = String::new();
// Create reversed iterators for both binary strings.
let (mut a, mut b) = (a.chars().rev(), b.chars().rev());
while let Some(a) = a.next() {
// Safe to unwrap since we know both iterators will be the same length.
let b = b.next().unwrap();
match (a, b) {
('1', '1') => {
// For 1 + 1, if we need to carry it will be 01 + 01 -> 10 + 01 -> 11.
// And otherwise it will be 01 + 01 -> 10, and carry next digit.
if carry {
sum.push('1');
} else {
sum.push('0');
carry = true;
}
}
// For 1 + 0 (and associatively 0 + 1), if we need to carry it's the same
// as 01 + 01 -> 10. And keep the carry set.
// And otherwise it will just be 01 + 00 -> 01.
('1', '0') | ('0', '1') => {
if carry {
sum.push('0');
} else {
sum.push('1');
}
}
// For 0 + 0, if we need to carry it results in 1 and otherwise 0.
('0', '0') => {
if carry {
sum.push('1');
carry = false;
} else {
sum.push('0');
}
}
_ => unreachable!(),
}
}
// And if the final digits required carrying, add the 1 here at the end.
if carry {
sum.push('1');
}
sum.chars().rev().collect()
}