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removeInvalidParentheses_301.java
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removeInvalidParentheses_301.java
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import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.Set;
/**
* 删除最小数量的无效括号,使得输入的字符串有效,返回所有可能的结果。
说明: 输入可能包含了除 ( 和 ) 以外的字符。
示例 1:
输入: "()())()"
输出: ["()()()", "(())()"]
示例 2:
输入: "(a)())()"
输出: ["(a)()()", "(a())()"]
示例 3:
输入: ")("
输出: [""]
*/
//回溯加括号判断
class removeInvalidParentheses_301 {
Set<String> set = new HashSet<>();
public List<String> removeInvalidParentheses(String s) {
char[] str = s.toCharArray();
int left = 0;
int right = 0;
for (char c : str) {
if (c == '(') {
left++;
}
else if (c == ')') {
if (left > 0) {
left--;
}
else {
right++;
}
}
}
StringBuffer buffer = new StringBuffer();
dfs(s, 0, 0, 0, left, right, buffer);
return new ArrayList<String> (set);
}
private void dfs(
String s,
int index,
int leftCount,
int rightCount,
int leftDelete,
int rightDelete,
StringBuffer buffer)
{
if (index == s.length()) {
if (leftDelete == 0 && rightDelete == 0) {
this.set.add(buffer.toString());
}
}
else {
if ((s.charAt(index) == '(' && leftDelete > 0) || (s.charAt(index) == ')' && rightDelete > 0)) {
dfs(s,
index+1,
leftCount,
rightCount,
s.charAt(index) == '('?leftDelete-1:leftDelete,
s.charAt(index) == ')'?rightDelete-1:rightDelete,
buffer);
}
buffer.append(s.charAt(index));
if (s.charAt(index) != '(' && s.charAt(index) != ')') {
dfs(s, index+1, leftCount, rightCount, leftDelete, rightDelete, buffer);
} else if (s.charAt(index) == '(') {
dfs(s, index+1, leftCount+1, rightCount, leftDelete, rightDelete, buffer);
} else if (leftCount > rightCount) {
dfs(s, index+1, leftCount, rightCount+1, leftDelete, rightDelete, buffer);
}
buffer.deleteCharAt(buffer.length()-1);
}
}
}