Remove All Adjacent Duplicates in String II — Stack with Counts

# Python
def removeDuplicates(s, k):
    stack = []  # (char, count)
    for c in s:
        if stack and stack[-1][0] == c:
            stack[-1] = (c, stack[-1][1]+1)
            if stack[-1][1] == k: stack.pop()
        else:
            stack.append((c, 1))
    return ''.join(c*cnt for c, cnt in stack)

// Java
public String removeDuplicates(String s, int k) {
    Deque<int[]> stack = new ArrayDeque<>(); // [char, count]
    for (char c : s.toCharArray()) {
        if (!stack.isEmpty() && stack.peek()[0]==c) {
            stack.peek()[1]++;
            if (stack.peek()[1]==k) stack.pop();
        } else stack.push(new int[]{c, 1});
    }
    StringBuilder sb = new StringBuilder();
    for (int[] pair : stack) for (int i=0;i<pair[1];i++) sb.append((char)pair[0]);
    return sb.reverse().toString();
}