Compilare: main.cpp: In function 'void solve()': main.cpp:22:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < expr.length(); i++){ ~~^~~~~~~~~~~~~~~ main.cpp:32:57: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(expr[i] >= '0' && expr[i] <= '9' && i < expr.length()){ ~~^~~~~~~~~~~~~~~ main.cpp:37:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(i < expr.length() && expr[i] >= 'a' && expr[i] <= 'z') ~~^~~~~~~~~~~~~~~ main.cpp:39:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] else if(i <= expr.length()){ ~~^~~~~~~~~~~~~~~~ main.cpp:40:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(i < expr.length()) ~~^~~~~~~~~~~~~~~ main.cpp: In function 'void task2()': main.cpp:80:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < v.size(); i++) ~~^~~~~~~~~~