Compilare: main.cpp: In function 'void pre()': main.cpp:10:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=1;i<strlen(s1);i++) ~^~~~~~~~~~~ main.cpp: In function 'int main()': main.cpp:23:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<strlen(s2);i++) ~^~~~~~~~~~~ main.cpp:29:13: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(j==strlen(s1)) ~^~~~~~~~~~~~