Compilare: user.cpp: In function ‘void rec(int)’: user.cpp:34:10: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(k == sir.size()) ~~^~~~~~~~~~~~~ user.cpp: In function ‘int main()’: user.cpp:64:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0; i<sir.size(); ++i) ~^~~~~~~~~~~ user.cpp:73:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(ap[c-'a']>sir.size()/2) ~~~~~~~~~^~~~~~~~~~~~~ user.cpp:61:19: warning: iteration 50 invokes undefined behavior [-Waggressive-loop-optimizations] ap[i] = 0; ~~~~~~^~~ user.cpp:60:23: note: within this loop for(int i=0; i<=50; ++i) ~^~~~