Description
Given a string s that contains parentheses and letters, remove the minimum number of invalid parentheses to make the input string valid.
Return a list of unique strings that are valid with the minimum number of removals. You may return the answer in any order.
Example 1:
Input: s = "()())()"
Output: ["(())()","()()()"]
Example 2:
Input: s = "(a)())()"
Output: ["(a())()","(a)()()"]
Example 3:
Input: s = ")("
Output: [""]
Constraints:
1 <= s.length <= 25s consists of lowercase English letters and parentheses '(' and ')'.- There will be at most
20 parentheses in s.
Solutions
Solution 1
PythonJavaC++Go
class Solution:
def removeInvalidParentheses(self, s: str) -> List[str]:
def dfs(i, l, r, lcnt, rcnt, t):
if i == n:
if l == 0 and r == 0:
ans.add(t)
return
if n - i < l + r or lcnt < rcnt:
return
if s[i] == '(' and l:
dfs(i + 1, l - 1, r, lcnt, rcnt, t)
elif s[i] == ')' and r:
dfs(i + 1, l, r - 1, lcnt, rcnt, t)
dfs(i + 1, l, r, lcnt + (s[i] == '('), rcnt + (s[i] == ')'), t + s[i])
l = r = 0
for c in s:
if c == '(':
l += 1
elif c == ')':
if l:
l -= 1
else:
r += 1
ans = set()
n = len(s)
dfs(0, l, r, 0, 0, '')
return list(ans)(code-box)
class Solution {
private String s;
private int n;
private Set<String> ans = new HashSet<>();
public List<String> removeInvalidParentheses(String s) {
this.s = s;
this.n = s.length();
int l = 0, r = 0;
for (char c : s.toCharArray()) {
if (c == '(') {
++l;
} else if (c == ')') {
if (l > 0) {
--l;
} else {
++r;
}
}
}
dfs(0, l, r, 0, 0, "");
return new ArrayList<>(ans);
}
private void dfs(int i, int l, int r, int lcnt, int rcnt, String t) {
if (i == n) {
if (l == 0 && r == 0) {
ans.add(t);
}
return;
}
if (n - i < l + r || lcnt < rcnt) {
return;
}
char c = s.charAt(i);
if (c == '(' && l > 0) {
dfs(i + 1, l - 1, r, lcnt, rcnt, t);
}
if (c == ')' && r > 0) {
dfs(i + 1, l, r - 1, lcnt, rcnt, t);
}
int x = c == '(' ? 1 : 0;
int y = c == ')' ? 1 : 0;
dfs(i + 1, l, r, lcnt + x, rcnt + y, t + c);
}
}(code-box)
class Solution {
public:
vector<string> removeInvalidParentheses(string s) {
unordered_set<string> ans;
int l = 0, r = 0, n = s.size();
for (char& c : s) {
if (c == '(') {
++l;
} else if (c == ')') {
if (l) {
--l;
} else {
++r;
}
}
}
function<void(int, int, int, int, int, string)> dfs;
dfs = [&](int i, int l, int r, int lcnt, int rcnt, string t) {
if (i == n) {
if (l == 0 && r == 0) {
ans.insert(t);
}
return;
}
if (n - i < l + r || lcnt < rcnt) {
return;
}
if (s[i] == '(' && l) {
dfs(i + 1, l - 1, r, lcnt, rcnt, t);
}
if (s[i] == ')' && r) {
dfs(i + 1, l, r - 1, lcnt, rcnt, t);
}
int x = s[i] == '(' ? 1 : 0;
int y = s[i] == ')' ? 1 : 0;
dfs(i + 1, l, r, lcnt + x, rcnt + y, t + s[i]);
};
dfs(0, l, r, 0, 0, "");
return vector<string>(ans.begin(), ans.end());
}
};(code-box)
func removeInvalidParentheses(s string) []string {
vis := map[string]bool{}
l, r, n := 0, 0, len(s)
for _, c := range s {
if c == '(' {
l++
} else if c == ')' {
if l > 0 {
l--
} else {
r++
}
}
}
var dfs func(i, l, r, lcnt, rcnt int, t string)
dfs = func(i, l, r, lcnt, rcnt int, t string) {
if i == n {
if l == 0 && r == 0 {
vis[t] = true
}
return
}
if n-i < l+r || lcnt < rcnt {
return
}
if s[i] == '(' && l > 0 {
dfs(i+1, l-1, r, lcnt, rcnt, t)
}
if s[i] == ')' && r > 0 {
dfs(i+1, l, r-1, lcnt, rcnt, t)
}
x, y := 0, 0
if s[i] == '(' {
x = 1
} else if s[i] == ')' {
y = 1
}
dfs(i+1, l, r, lcnt+x, rcnt+y, t+string(s[i]))
}
dfs(0, l, r, 0, 0, "")
ans := make([]string, 0, len(vis))
for v := range vis {
ans = append(ans, v)
}
return ans
}(code-box)
