Remove All Occurrences of a Given Character using Two Pointer Approach

 

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Problem: Remove All Occurrences of a Given Character

Problem Statement:

Given a string s and a character ch, remove all occurrences of ch from s using the two-pointer approach.

Example 1:

Input: "apple", 'p'
Output: "ale"

Example 2:

Input: "banana", 'a'
Output: "bnn"

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Java Solution (Two-Pointer Approach)

public class RemoveCharacter {
    public static String removeChar(String s, char ch) {
        char[] chars = s.toCharArray();
        int j = 0; // Pointer for placing valid characters

        for (int i = 0; i < chars.length; i++) {
            if (chars[i] != ch) {
                chars[j] = chars[i];
                j++; // Move valid character index forward
            }
        }

        return new String(chars, 0, j);
    }

    public static void main(String[] args) {
        System.out.println(removeChar("apple", 'p'));  // Output: "ale"
        System.out.println(removeChar("banana", 'a')); // Output: "bnn"
    }
}

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Explanation (Two-Pointer Approach)

1. Use Two Pointers:

   • i iterates through the original string.
   • j keeps track of the next position for valid characters.

2. Skip the Character to Remove:

   • If s[i] is not equal to ch, move it to j position.

3. Return New String Without the Removed Characters.

Time Complexity: O(n) (single pass through the string)
Space Complexity: O(n) (output string storage)

🔥 This is an easy and efficient way to remove a character from a string using two pointers! 🚀

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