Compilare: main.cpp: In function 'void buildGraph()': main.cpp:76:25: warning: unused variable 'x' [-Wunused-variable] for (char i='a', j, x; i<='z'; ++i) { ^ main.cpp: In function 'void solveInput()': main.cpp:112:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=0; i<letter.size(); ++i, output << ' ') ~^~~~~~~~~~~~~~