Language: C++

#include <stdio.h>
#include <string.h>
#include <vector>

int N;
char s[112345];
char temp[112345];
std::vector<std::string>res;
bool Is_ans_flag = true;
char ans[112345] = "-1";

void f(int pos, char string[])
{
	if (pos >= N)
	{
		std::string tete = string;
		res.push_back(tete);
	}
	else
	{
		if (s[pos] == 'o')
		{
			temp[(pos - 1) % N] = 'S', temp[pos] = 'S', temp[(pos + 1) % N] = 'S';
			f(pos + 2, temp);
			temp[(pos - 1) % N] = 'W', temp[pos] = 'S', temp[(pos + 1) % N] = 'W';
			f(pos + 2, temp);
			temp[(pos - 1) % N] = 'S', temp[pos] = 'W', temp[(pos + 1) % N] = 'W';
			f(pos + 2, temp);
			temp[(pos - 1) % N] = 'W', temp[pos] = 'W', temp[(pos + 1) % N] = 'S';
			f(pos + 2, temp);
		}
		if (s[pos] == 'x')
		{
			temp[(pos - 1) % N] = 'S', temp[pos] = 'S', temp[(pos + 1) % N] = 'W';
			f(pos + 2, temp);
			temp[(pos - 1) % N] = 'W', temp[pos] = 'S', temp[(pos + 1) % N] = 'S';
			f(pos + 2, temp);
			temp[(pos - 1) % N] = 'S', temp[pos] = 'W', temp[(pos + 1) % N] = 'S';
			f(pos + 2, temp);
			temp[(pos - 1) % N] = 'W', temp[pos] = 'W', temp[(pos + 1) % N] = 'W';
			f(pos + 2, temp);
		}
	}
}

int main(void)
{
	scanf("%d%s", &N, s);
	f(1, "");
	for (int i = 0; i < res.size(); ++i)
	{
		Is_ans_flag = true;
		for (int j = 1; j < N; ++j)
		{
			if (s[j] == 'o')
			{
				if (res[i][j] == 'S')
				{
					if (res[i][(j - 1) % N] != res[i][(j + 1) % N])
					{
						Is_ans_flag = false;
						break;
					}
				}
				if (res[i][j] == 'W')
				{
					if (res[i][(j - 1) % N] == res[i][(j + 1) % N])
					{
						Is_ans_flag = false;
						break;
					}
				}
			}
			if (s[j] == 'x')
			{
				if (res[i][j] == 'S')
				{
					if (res[i][(j - 1) % N] == res[i][(j + 1) % N])
					{
						Is_ans_flag = false;
						break;
					}
				}
				if (res[i][j] == 'W')
				{
					if (res[i][(j - 1) % N] != res[i][(j + 1) % N])
					{
						Is_ans_flag = false;
						break;
					}
				}
			}
		}
		if (Is_ans_flag == true)
		{
			res[i].copy(ans, res[i].size());
			break;
		}
	}

	printf("%s\n", ans);
	return 0;
}

Compiler output:
a.cc:8:18: error: 'string' is not a member of 'std'
    8 | std::vector<std::string>res;
      |                  ^~~~~~
a.cc:4:1: note: 'std::string' is defined in header '<string>'; this is probably fixable by adding '#include <string>'
    3 | #include <vector>
  +++ |+#include <string>
    4 | 
a.cc:8:24: error: template argument 1 is invalid
    8 | std::vector<std::string>res;
      |                        ^
a.cc:8:24: error: template argument 2 is invalid
a.cc: In function 'void f(int, char*)':
a.cc:16:22: error: 'string' is not a member of 'std'
   16 |                 std::string tete = string;
      |                      ^~~~~~
a.cc:16:22: note: 'std::string' is defined in header '<string>'; this is probably fixable by adding '#include <string>'
a.cc:17:21: error: request for member 'push_back' in 'res', which is of non-class type 'int'
   17 |                 res.push_back(tete);
      |                     ^~~~~~~~~
a.cc:17:31: error: 'tete' was not declared in this scope
   17 |                 res.push_back(tete);
      |                               ^~~~
a.cc: In function 'int main()':
a.cc:49:14: warning: ISO C++ forbids converting a string constant to 'char*' [-Wwrite-strings]
   49 |         f(1, "");
      |              ^~
a.cc:50:33: error: request for member 'size' in 'res', which is of non-class type 'int'
   50 |         for (int i = 0; i < res.size(); ++i)
      |                                 ^~~~
a.cc:57:40: error: invalid types 'int[int]' for array subscript
   57 |                                 if (res[i][j] == 'S')
      |                                        ^
a.cc:59:48: error: invalid types 'int[int]' for array subscript
   59 |                                         if (res[i][(j - 1) % N] != res[i][(j + 1) % N])
      |                                                ^
a.cc:59:71: error: invalid types 'int[int]' for array subscript
   59 |                                         if (res[i][(j - 1) % N] != res[i][(j + 1) % N])
      |                                                                       ^
a.cc:65:40: error: invalid types 'int[int]' for array subscript
   65 |                                 if (res[i][j] == 'W')
      |                                        ^
a.cc:67:48: error: invalid types 'int[int]' for array subscript
   67 |                                         if (res[i][(j - 1) % N] == res[i][(j + 1) % N])
      |                                                ^
a.cc:67:71: error: invalid types 'int[int]' for array subscript
   67 |                                         if (res[i][(j - 1) % N] == res[i][(j + 1) % N])
      |                                                                       ^
a.cc:76:40: error: invalid types 'int[int]' for array subscript
   76 |                                 if (res[i][j] == 'S')
      |                                        ^
a.cc:78:48: error: invalid types 'int[int]' for array subscript
   78 |                                         if (res[i][(j - 1) % N] == res[i][(j + 1) % N])
      |                                                ^
a.cc:78:71: error: invalid types 'int[int]' for array subscript
   78 |                                         if (res[i][(j - 1) % N] == res[i][(j + 1) % N])
      |                                                                       ^
a.cc:84:40: error: invalid types 'int[int]' for array subscript
   84 |                                 if (res[i][j] == 'W')
      |                                        ^
a.cc:86:48: error: invalid types 'int[int]' for array subscript
   86 |                                         if (res[i][(j - 1) % N] != res[i][(j + 1) % N])
      |                                                ^
a.cc:86:71: error: invalid types 'int[int]' for array subscript
   86 |                                         if (res[i][(j - 1) % N] != res[i][(j + 1) % N])
      |                                                                       ^
a.cc:96:28: error: invalid types 'int[int]' for array subscript
   96 |                         res[i].copy(ans, res[i].size());
      |                            ^
a.cc:96:45: error: invalid types 'int[int]' for array subscript
   96 |                         res[i].copy(ans, res[i].size());
      |                                             ^