56 lines
1.1 KiB
Java
56 lines
1.1 KiB
Java
package ProjectEuler;
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/**
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* The sum of the primes below 10 is 2 + 3 + 5 + 7 = 17.
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*
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* <p>Find the sum of all the primes below two million.
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*
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* <p>link: https://projecteuler.net/problem=10
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*/
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public class Problem10 {
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public static void main(String[] args) {
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long[][] testNumbers = {
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{2000000, 142913828922L},
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{10000, 5736396},
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{5000, 1548136},
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{1000, 76127},
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{10, 17},
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{7, 10}
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};
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for (long[] testNumber : testNumbers) {
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assert solution1(testNumber[0]) == testNumber[1];
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}
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}
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/***
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* Checks if a number is prime or not
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* @param n the number
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* @return {@code true} if {@code n} is prime
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*/
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private static boolean isPrime(int n) {
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if (n == 2) {
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return true;
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}
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if (n < 2 || n % 2 == 0) {
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return false;
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}
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for (int i = 3, limit = (int) Math.sqrt(n); i <= limit; i += 2) {
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if (n % i == 0) {
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return false;
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}
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}
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return true;
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}
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private static long solution1(long n) {
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long sum = 0;
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for (int i = 2; i < n; ++i) {
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if (isPrime(i)) {
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sum += i;
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}
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}
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return sum;
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}
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}
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