Given a string without spaces, the task is to remove duplicates from it.
Note: The original order of characters must be kept the same.
Example 1:
Input: S = "zvvo"
Output: "zvo"
Explanation: Only keep the first
occurrence
Example 2:
Input: S = "gfg"
Output: gf
Explanation: Only keep the first
occurrence
Your task:
Your task is to complete the function removeDups() which takes a single string as input and returns the string. You need not take any input or print anything.

Expected Time Complexity: O(|s|)
Expected Auxiliary Space: O(constant)
Constraints:
1 <= |S| <= 10^{5}
S conatins lowercase english alphabets

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