2520 is the smallest number that can be divided by each of the numbers from 1 to 10 without any remainder.
What is the smallest positive number that is evenly divisible by all of the numbers from 1 to 20?
int times = 0;
for (int i=1; i<1000000000; i++) {
for (int j=1; j<=20; j++) {
if (i%j==0) {
times++;
}
}
if (times==20) {
System.out.println(i);
break;
}
times = 0;
}
Lösung: 232792560
A palindromic number reads the same both ways. The largest palindrome made from the product of two 2-digit numbers is 9009 = 91 × 99.
Find the largest palindrome made from the product of two 3-digit numbers.
int number1;
int number2;
int highest = 0;
int temp;
for (number1=100; number1<999; number1++) {
for (number2=100; number2<999; number2++) {
temp = number1*number2;
if (Integer.toString(temp).equals(new StringBuffer(Integer.toString(temp)).reverse().toString())) {
if (temp>highest) {
highest = temp;
System.out.println(number1 + " * " + number2 + " = " + highest);
}
}
}
}
Lösung: 906609
The prime factors of 13195 are 5, 7, 13 and 29.
What is the largest prime factor of the number 600851475143 ?
final long value = 600851475143L;
long temp = value;
long prime = 2;
while (temp>1L) {
if (temp%prime==0) {
System.out.println(prime);
temp = temp/prime;
} else {
prime++;
}
}
Lösung: 6857
Each new term in the Fibonacci sequence is generated by adding the previous two terms. By starting with 1 and 2, the first 10 terms will be:
1, 2, 3, 5, 8, 13, 21, 34, 55, 89, …
By considering the terms in the Fibonacci sequence whose values do not exceed four million, find the sum of the even-valued terms.
int x = 0;
int y = 1;
int limit = 4000000;
int result = 0;
int temp;
while (y<limit) {
temp = x + y;
x = y;
y = temp;
if (y%2==0) {
result += y;
}
}
System.out.println(result);
Lösung: 4613732
If we list all the natural numbers below 10 that are multiples of 3 or 5, we get 3, 5, 6 and 9. The sum of these multiples is 23.
Find the sum of all the multiples of 3 or 5 below 1000.
int result = 0;
for (int i=0; i<1000; i++) {
if (i%3==0 || i%5==0) {
result += i;
}
}
System.out.println(result);
Lösung: 233168