Compilare: main.cpp: In function 'bool valid(int)': main.cpp:22:9: warning: this 'if' clause does not guard... [-Wmisleading-indentation] if(st[i]==st[j] || st[i]>st[i+1]) ^~ main.cpp:23:18: note: ...this statement, but the latter is misleadingly indented as if it is guarded by the 'if' return 0;return 1; ^~~~~~ main.cpp: In function 'void back()': main.cpp:55:15: warning: suggest explicit braces to avoid ambiguous 'else' [-Wparentheses] if(valid(j)) ^ main.cpp:50:9: warning: unused variable 'i' [-Wunused-variable] int i,j=1; ^