Compilare: user.cpp: In function ‘int main()’: user.cpp:20:24: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(u<=strlen(S)-1) ^ user.cpp:21:81: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] {while(S[u]<S[u-1]&&S[u]<S[u+1]||S[u]>S[u-1]&&S[u]>S[u+1]&&u<=strlen(S)-1) ^ user.cpp:21:27: warning: suggest parentheses around ‘&&’ within ‘||’ [-Wparentheses] {while(S[u]<S[u-1]&&S[u]<S[u+1]||S[u]>S[u-1]&&S[u]>S[u+1]&&u<=strlen(S)-1) ^ user.cpp:37:34: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=1;i<=strlen(S)-2;i++) ^