LeetCode-in-Java
844. Backspace String Compare
Easy
Given two strings s and t, return true if they are equal when both are typed into empty text editors. '#' means a backspace character.
Note that after backspacing an empty text, the text will continue empty.
Example 1:
Input: s = “ab#c”, t = “ad#c”
Output: true
Explanation: Both s and t become “ac”.
Example 2:
Input: s = “ab##”, t = “c#d#”
Output: true
Explanation: Both s and t become “”.
Example 3:
Input: s = “a#c”, t = “b”
Output: false
Explanation: s becomes “c” while t becomes “b”.
Constraints:
1 <= s.length, t.length <= 200sandtonly contain lowercase letters and'#'characters.
Follow up: Can you solve it in O(n) time and O(1) space?
Solution
public class Solution {
public boolean backspaceCompare(String s, String t) {
return cmprStr(s).equals(cmprStr(t));
}
private String cmprStr(String str) {
StringBuilder res = new StringBuilder();
int count = 0;
for (int i = str.length() - 1; i >= 0; i--) {
char currChar = str.charAt(i);
if (currChar == '#') {
count++;
} else {
if (count > 0) {
count--;
} else {
res.append(currChar);
}
}
}
return res.toString();
}
}