#include <stdio.h>
#include <math.h>

int board[12] = { 0 },N,result;

int collision(int i) { 
    int k = 0, promising = 1;
    if (i == 0) 
        return promising;

    while (k < i && promising) {
        if (board[i] == board[k] ||  (abs(board[i] - board[k]) == abs(i - k)) )
            promising = 0;
        k++;
    }
    return promising;
}
int queen(int y) {
    int i;
    if (y == N)
        result++;
    else
        for (i = 0; i < N; i++) {
            board[y] = i;
            if (collision(y)) 
                queen(y + 1);
        }
}
int main() {
    unsigned int C;
    scanf("%d", &C);

    while (C--) {
        result = 0;
        scanf("%d", &N);
        queen(0);
        printf("%d\n", result);
    }   
}

submission.c: In function ‘collision’:
submission.c:12:3: error: implicit declaration of function ‘abs’ [-Wimplicit-function-declaration]
if (board[i] == board[k] || (abs(board[i] - board[k]) == abs(i - k)) )
^
submission.c: In function ‘main’:
submission.c:32:2: warning: format ‘%d’ expects argument of type ‘int *’, but argument 2 has type ‘unsigned int *’ [-Wformat=]
scanf("%d", &C);
^
submission.c:32:2: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result [-Wunused-result]
submission.c:35:3: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result [-Wunused-result]
scanf("%d", &N);
^

VS2015와 ideone으로 테스트했을땐 오류가없는데
답변제출을하면 저런 오류를 뱉습니다
math함수가 제대로 include안되어 abs함수가 안불러지는것같은데
다른 분들이 쓴걸보면 math함수를 씀에도 잘 되고 scanf부분도 큰문제는 없는것 같은데
제가 어떤부분에서 틀린지좀 여쭤봅니다