DNA-题解(C语言代码)

我的提交一直报错，大佬可以帮我找一下错误原因吗，谢谢
#include<stdio.h>
int main() {
	int N,a,b;
	scanf("%d", &N);
	while (N-- > 0) {
		scanf("%d%d", &a, &b);
		char image[40][40] = {' '};
		for (int i = 0; i < a; i++) {
			image[i][i] = 'X';
			image[i][a - 1 - i] = 'X';
		}
		for (int j = 1; j <= b; j++) {
			if (j == 1) {
				for (int i = 0; i < a; i++) {
					for (int k = 0; k < a; k++)
						printf("%c", image[i][k]);
					printf("\n");
				}
			}
			else {
				for (int i = 1; i < a; i++) {
					for (int k = 0; k < a; k++)
						printf("%c", image[i][k]);
					printf("\n");
				}
			}
		}
		   printf("\n");
	}