View Compilation Error

0_0_21148537_31281.cpp: In function 'int main()':
0_0_21148537_31281.cpp:19:40: error: 'k' was not declared in this scope
             printf(j==0?"%d\n":"%d ",a[k]);//k==j时跳出内层的for循环，此时a[k]就是最后一个数，直接输出。进入下一个外层for循环。  
                                        ^