LeetCode Entry
1544. Make The String Great
Remove lowercase-uppercase pairs
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Problem TLDR
Remove lowercase-uppercase pairs #easy
Intuition
Consider example:
EbBe
**
E e
After removing the middle bB we have to consider the remaining Ee. We can use Stack to do that.
Approach
In Kotlin: no need for Stack, just use StringBuilder.
In Rust: Vec can be used as a Stack. There is no to_lowercase method returning a char, however there is a to_ascii_lowercase.
Complexity
-
Time complexity: \(O(n)\)
-
Space complexity: \(O(n)\)
Code
fun makeGood(s: String) = buildString {
for (c in s)
if (length > 0 && c != get(lastIndex) &&
c.lowercase() == get(lastIndex).lowercase()
) setLength(lastIndex) else append(c)
}
pub fn make_good(s: String) -> String {
let mut stack = vec![];
for c in s.chars() {
if stack.is_empty() { stack.push(c) }
else {
let p = *stack.last().unwrap();
if c != p && c.to_lowercase().eq(p.to_lowercase()) {
stack.pop();
} else { stack.push(c) }
}
}
stack.iter().collect()
}