View Compilation Error

0_0_37482345_29998.cpp: In function 'int main()':
0_0_37482345_29998.cpp:13:21: error: 'str' was not declared in this scope
         a[i][strlen(str)]= ' ';
                     ^
0_0_37482345_29998.cpp:15:26: error: 'len' was not declared in this scope
         for(k = 0 ; k <= len ; k++)
                          ^