public static List <string> GenerateValidParentheses(int num)
{
List <string> result = new ();
Queue <ParenthesesString> queue = new();
queue.Enqueue(new ParenthesesString("", 0, 0));
while (queue.Count != 0)
{
ParenthesesString ps = queue.Dequeue();
// if we've reached the maximum number of open and close parentheses, add to the result
if (ps.OpenCount == num && ps.CloseCount == num)
{
result.Add(ps.Str);
}
else
{
if (ps.OpenCount < num) // if we can add an open parentheses, add it
{
queue.Enqueue(new ParenthesesString(ps.Str + "(", ps.OpenCount + 1, ps.CloseCount));
}
if (ps.OpenCount > ps.CloseCount) // if we can add a close parentheses, add it
{
queue.Enqueue(new ParenthesesString(ps.Str + ")", ps.OpenCount, ps.CloseCount + 1));
}
}
}
return(result);
}
public static List <String> generateValidParentheses(int num)
{
List <String> result = new List <String>();
// TODO: Write your code here
Queue <ParenthesesString> queue = new Queue <ParenthesesString>();
queue.Enqueue(new ParenthesesString()
{
OpenCount = 0, CloseCount = 0, PartialString = ""
});
while (queue.Count > 0)
{
int m = queue.Count;
for (int j = 0; j < m; j++)
{
ParenthesesString ps = queue.Dequeue();
if (ps.OpenCount == num && ps.CloseCount == num)
{
result.Add(ps.PartialString);
}
else
{
ParenthesesString rs = new ParenthesesString()
{
OpenCount = ps.OpenCount,
CloseCount = ps.CloseCount,
PartialString = ps.PartialString
};
if (ps.OpenCount < num)
{
ps.OpenCount += 1;
ps.PartialString += '(';
queue.Enqueue(ps);
}
if (rs.CloseCount < rs.OpenCount)
{
rs.CloseCount += 1;
rs.PartialString += ')';
queue.Enqueue(rs);
}
}
}
}
/*
** My original solution by noting that counting is time consuming task
** result.Add(String.Empty);
** for (int i = 0; i < num*2; i ++) {
** int m = result.Count;
** for (int j = 0; j < m; j++) {
** string l = result[j] + "(";
** string r = result[j] + ")";
** bool modifiedInPlace = false;
** if (l.Count(c=>{return c=='(';}) <= num) {
** result[j] = l;
** modifiedInPlace = true;
** }
** if (r.Count(c=>{return c == ')';}) <= r.Length/2) {
** if (modifiedInPlace) result.Add(r);
** else result[j] = r;
** }
** }
** }
*/
return(result);
}
