int convertDecimalToOctal(int decimalNumber);
int main()
{
int decimalNumber;

printf("输入一个十进制数: ");
scanf("%d", &decimalNumber);

printf("十进制数 %d 转换为八进制为 %d", decimalNumber, convertDecimalToOctal(decimalNumber));

return 0;
}

int convertDecimalToOctal(int decimalNumber)
{
int octalNumber = 0, i = 1;

while (decimalNumber != 0)
{
octalNumber += (decimalNumber % 8) * i;
decimalNumber /= 8;
i *= 10;
}

return octalNumber;
}

long long convertOctalToDecimal(int octalNumber);
int main()
{
int octalNumber;

printf("输入一个八进制数: ");
scanf("%d", &octalNumber);

printf("八进制数 %d 转换为十进制为 %lld", octalNumber, convertOctalToDecimal(octalNumber));

return 0;
}

long long convertOctalToDecimal(int octalNumber)
{
int decimalNumber = 0, i = 0;

while(octalNumber != 0)
{
decimalNumber += (octalNumber%10) * pow(8,i);
++i;
octalNumber/=10;
}

i = 1;

return decimalNumber;
}