Compilare: main.cpp: In function 'void prefix_function()': main.cpp:11:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=1;i<b.size();i++) ~^~~~~~~~~ main.cpp: In function 'int main()': main.cpp:27:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<b.size();i++) ~^~~~~~~~~ main.cpp:28:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(pi[i]==a.size()) ~~~~~^~~~~~~~~~ main.cpp:32:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<b.size()&&nr<1000;i++) ~^~~~~~~~~ main.cpp:33:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(pi[i]==a.size()) ~~~~~^~~~~~~~~~