leetcode 1209. Remove All Adjacent Duplicates in String II
Given a string s, a k duplicate removal consists of choosing k adjacent and equal letters from s and removing them causing the left and the right side of the deleted substring to concatenate together.We repeatedly make k duplicate removals on s until we no longer can.
Return the final string after all such duplicate removals have been made.
It is guaranteed that the answer is unique.
Example 1:
Input: s = "abcd", k = 2
Output: "abcd"
Explanation: There's nothing to delete.
Example 2:
Input: s = "deeedbbcccbdaa", k = 3
Output: "aa"
Explanation:
First delete "eee" and "ccc", get "ddbbbdaa"
Then delete "bbb", get "dddaa"
Finally delete "ddd", get "aa"
Example 3:
Input: s = "pbbcggttciiippooaais", k = 2
Output: "ps"
Constraints:
1 <= s.length <= 10^5
2 <= k <= 10^4
s only contains lower case English letters.
class Solution {
public String removeDuplicates(String s, int k) {
Stack <Character> stack_c = new Stack<>();
Stack <Integer> stack_n = new Stack<>();
for(int i = 0; i < s.length(); i++){
if(!stack_c.isEmpty() && stack_c.peek() == s.charAt(i)){
stack_n.push(stack_n.peek()+1);
}else{
stack_n.push(1);
}
stack_c.push(s.charAt(i));
if(stack_n.peek() == k){
for(int j = 0; j< k ; j++){
stack_n.pop();
stack_c.pop();
}
}
}
StringBuilder ret = new StringBuilder();
while(!stack_c.isEmpty()){
ret.append(stack_c.pop());
}
return ret.reverse().toString();
}
}
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