Given a string s of '('
, ')'
and lowercase English characters.
Your task is to remove the minimum number of parentheses ( '('
or ')'
, in any positions ) so that the resulting parentheses string is valid and return any valid string.
Formally, a parentheses string is valid if and only if:
- It is the empty string, contains only lowercase characters, or
- It can be written as
AB
(A
concatenated withB
), whereA
andB
are valid strings, or - It can be written as
(A)
, whereA
is a valid string.
Example 1:
Input: s = "lee(t(c)o)de)"
Output: "lee(t(c)o)de"
Explanation: "lee(t(co)de)" , "lee(t(c)ode)" would also be accepted.
Example 2:
Input: s = "a)b(c)d"
Output: "ab(c)d"
Example 3:
Input: s = "))(("
Output: ""
Explanation: An empty string is also valid.
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Constraints:文章来源地址https://www.toymoban.com/news/detail-744824.html
1 <= s.length <= 105
-
s[i]
is either'('
,')'
, or lowercase English letter.
class Solution {
public String minRemoveToMakeValid(String s) {
if(s == null || s.length() == 0){
return "";
}
//做括号的题一定要用栈,切记。这题用的是贪心算法,找到左括号,进栈,找到右括号,出栈,进栈出栈的都是char array的index。
char[] ans = s.toCharArray();
Stack<Integer> stack = new Stack<Integer>();
for(int i=0; i<ans.length; i++){
if(ans[i] == '('){
stack.push(i);
}
if(ans[i] == ')'){
if(stack.isEmpty()){ //如果这个时候栈为空,更改右括号为空。
ans[i] = ' ';
}else{
stack.pop();
}
}
}
while(!stack.isEmpty()){ //如果最后还剩左括号,把左括号都置为空
int index = stack.pop();
ans[index] = ' ';
}
String result = new String(ans);
result = result.replace(" ", "");
return result;
}
}
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