View Compilation Error

0_0_17137000_12566.cpp: In function 'int Change(int*, char*)':
0_0_17137000_12566.cpp:11:26: error: 'strlen' was not declared in this scope
  int i,k=0,len=strlen(str),t=1;
                          ^
0_0_17137000_12566.cpp:15:12: error: 't' was not declared in this scope
   { a[k++]=t; t=1;}
            ^
0_0_17137000_12566.cpp:17:3: error: 't' was not declared in this scope
   t++;
   ^
0_0_17137000_12566.cpp:19:7: error: 't' was not declared in this scope
  a[k]=t;
       ^