Question 2 :
Reverse Prefix of Word(Using Stack)
Given a 0-indexed string word and a character ch, reverse the segment of word that starts at index 0 and ends at the index of the first occurrence of ch (inclusive). If the character ch does not exist in word, do nothing.
For example, if word = “abcdefd” and ch = “d”, then you should reverse the segment that starts at 0 and ends at 3 (inclusive). The resulting string will be “dcbaefd”.
Return the resulting string.
a b c d e f d
0 1 2 3 4 5 6
d–>3
dcbaefd
Example 1:
Input: word = “abcdefd”, ch = “d”
Output: “dcbaefd”
Explanation: The first occurrence of “d” is at index 3.
Reverse the part of word from 0 to 3 (inclusive), the resulting string is “dcbaefd”.
Example 2:
Input: word = “xyxzxe”, ch = “z”
Output: “zxyxxe”
Explanation: The first and only occurrence of “z” is at index 3.
Reverse the part of word from 0 to 3 (inclusive), the resulting string is “zxyxxe”.
Example 3:
Input: word = “abcd”, ch = “z”
Output: “abcd”
Explanation: “z” does not exist in word.
You should not do any reverse operation, the resulting string is “abcd”.
Test Case 1 :
Input :
abcdefd
d
Output :
dcbaefd
Test Case 2 :
Input :
xyxzxe
z
Output :
zxyxxe
—————————————————–*/
import java.util.*;
class c
{
public static void main(String args[])
{
String word=”abcdefd”;
char ch=’d’;
Stack<Character> result=new Stack<>();
StringBuilder a=new StringBuilder();
int i=0;
while(i < word.length())//3<7
{
result.push(word.charAt(i));//d
if(word.charAt(i)==ch)//d==d
{
break;
}
i++;
}
while(!result.isEmpty())
{
a.append(result.pop());
}
a.append(word.substring(i+1));
System.out.println(a.toString());
}
}