[LeetCode] Backspace String Compare

Given two strings S and T, return 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 = "#a#c"
Output: true
Explanation: Both S and T become "c".

Example 4:

Input: S = "a#c", T = "b"
Output: false
Explanation: S becomes "c" while T becomes "b".

Note:

• 1 <= S.length <= 200
• 1 <= T.length <= 200
• S and T only contain lowercase letters and ‘#’ characters.

Follow up:

• Can you solve it in O(N) time and O(1) space?

解题思路: 扫描一次直接对原字符串进行退格然后比较

class {
public:
	bool backspaceCompare(string S, string T);
}

void backspaceHelper(string& s) {
	string::iterator it = s.begin();
	while (it != s.cend()) {
		if (*it == '#') {
			s.erase(it);
			if (it != s.begin()) {
				s.erase(it - 1);
				it--;
			}
			continue;
		}
		it++;
	}
}

bool
Solution::backspaceCompare(string S, string T) {
	backspaceHelper(S);
	backspaceHelper(T);
	return S == T;
}