String Manipulation

 Tom is a string freak. He has got sequences of words arr[] to manipulate. If in a sequence, two same words come together then Tom destroys each other. Find the number of words left in the sequence after this pairwise destruction. 


Examples:


Input: arr[] = ["ab", "aa", "aa", "bcd", "ab"]

Output: 3

Explanation: After the first iteration, we'll have: ab bcd ab. We can't further destroy more strings and hence we stop and the result is 3. 

Input: arr[] = ["tom", "jerry", "jerry", "tom"]

Output: 0

Explanation: After the first iteration, we'll have: tom tom. After the second iteration: 'empty-array' .Hence, the result is 0.

Expected Time Complexity: O(n)

Expected Auxiliary Space: O(n)


static int removeConsecutiveSame(String[] arr) {
    Stack<String> st = new Stack<>();

    for (int i = 0; i < arr.length; i++) {
        if (st.empty()) {
            st.push(arr[i]);
        } else {
            if (st.peek().equals(arr[i])) {
                st.pop(); // remove the last same item
            } else {
                st.push(arr[i]);
            }
        }
    }
    return st.size();
}

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