052 - N-Queens II

Follow up for N-Queens problem.

Now, instead outputting board configurations, return the total number of distinct solutions.





static int Q;
static int retcur;

int locok(char **queen, int cur, int b)
{
int i,j;
for(i = 0; i< cur; i++)
for(j = 0; j < Q; j++) {
if (queen[i][j] == 'Q') {
if (i == cur || j == b) return 0;
if (abs(i - cur) == abs(j - b)) return 0;
}
}
return 1;
}

void x8q(char **queen, int cur)
{
if (cur == Q) return;
if (cur == Q - 1) {
int i;
for(i = 0; i < Q;i ++) {
if (locok(queen, cur, i)) {
queen[cur][i] = 'Q';
retcur++;
queen[cur][i] = '.';
}
}
} else {
int i;
for(i = 0; i < Q; i ++) {
if (locok(queen, cur, i)) {
queen[cur][i] = 'Q';
x8q(queen, cur + 1);
queen[cur][i] = '.';
}
}
}
}

int totalNQueens(int n)
{
int i, j;
retcur = 0;

char *queen[100] = {0};
for (i = 0; i < n; i++) {
queen[i] = (char *)malloc(sizeof(char) * n);
memset(queen[i], '.', n);
}

Q = n;
x8q(queen, 0);
return retcur;
}


int totalNQueens(int n)
{
int ret[] = {0, 1, 0, 0, 2, 10, 4, 40, 92, 352, 724, 2680, 14200, 73712};
if (n <= 13) return ret
;
return -1;
}