Răspuns :
int permutarenr(int n){
int t=n,nr=0,d=1;
while(t>10){
nr+=(t%10)*d;
d*=10;
t/=10;
}
nr=nr*10+t;
return nr;
}
Poti incerca si asta (iti va trebui <cmath> dar daca vrei poti sa-ti faci singur functiile pow si log10 daca nu vrei sa folosesti alta librarie):
int f(int n)
{
int div = (float)pow(10, int(log10(n)));
return (n % div) * 10 + n / div;
}
int f(int n)
{
int div = (float)pow(10, int(log10(n)));
return (n % div) * 10 + n / div;
}