Easy to Understand For Beginners using Stack.
IntuitionMaintain a stack and check if last character is "Almost Equal"ApproachComplexity
Time complexity:
O(n)
Space complexity:
Code
# Intuition
<!-- Describe your first thoughts on how to solve this problem. -->
Maintain a stack and check if last character is "Almost Equal"
# Approach
<!-- Describe your approach to solving the problem. -->

# Complexity
- Time complexity:
<!-- Add your time complexity here, e.g. $$O(n)$$ -->
O(n)
- Space complexity:
<!-- Add your space complexity here, e.g. $$O(n)$$ -->

# Code
```java []
class Solution {
    public int removeAlmostEqualCharacters(String s) {
        int ans = 0;
        Stack<Character> stack = new Stack<>();
// Intialize a character stack and int ans to store ans.
        for (char c : s.toCharArray()) {
// If stack is empty add c to stack.
            if (stack.empty()) {
                stack.push(c);
            } else {
// Check if c is Almost Equal to top char in stack.
                if (Math.abs(c - stack.peek()) > 1) {
// If not almost equal add to stack.
                    stack.push(c);
                } else {
// If it is almost equal add a non-aplhabetic character eg: '0'.
// Increase ans by one.
                    stack.push('0');
                    ans++;
                }
            }
        }
        return ans;
    }
}
```
['String', 'Stack', 'Counting', 'Java']