/in/foo.c: In function 'bubbleSort':
/in/foo.c:5:8: warning: implicit declaration of function 'strlen' [-Wimplicit-function-declaration]
  int n=strlen(s);
        ^~~~~~
/in/foo.c:5:8: warning: incompatible implicit declaration of built-in function 'strlen'
/in/foo.c:5:8: note: include '<string.h>' or provide a declaration of 'strlen'