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Created Problem06 in Project Euler #1461

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Merged
realDuYuanChao merged 2 commits into from
Sep 17, 2020
Merged

Created Problem06 in Project Euler #1461

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Created Problem06 in ProjectEuler
realDuYuanChao Sep 16, 2020
a195c69
updating DIRECTORY.md
Sep 16, 2020
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1 change: 1 addition & 0 deletions DIRECTORY.md
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Expand Up @@ -204,6 +204,7 @@
* [Problem01](https://github.com/TheAlgorithms/Java/blob/master/ProjectEuler/Problem01.java)
* [Problem02](https://github.com/TheAlgorithms/Java/blob/master/ProjectEuler/Problem02.java)
* [Problem04](https://github.com/TheAlgorithms/Java/blob/master/ProjectEuler/Problem04.java)
* [Problem06](https://github.com/TheAlgorithms/Java/blob/master/ProjectEuler/Problem06.java)

## Searches
* [BinarySearch](https://github.com/TheAlgorithms/Java/blob/master/Searches/BinarySearch.java)
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46 changes: 46 additions & 0 deletions ProjectEuler/Problem06.java
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package ProjectEuler;

/**
* The sum of the squares of the first ten natural numbers is,
* 1^2 + 2^2 + ... + 10^2 = 385
* The square of the sum of the first ten natural numbers is,
* (1 + 2 + ... + 10)^2 = 552 = 3025
* Hence the difference between the sum of the squares of the first ten natural
* numbers and the square of the sum is 3025 − 385 = 2640.
* Find the difference between the sum of the squares of the first N natural
* numbers and the square of the sum.
* <p>
* link: https://projecteuler.net/problem=6
*/
public class Problem06 {
public static void main(String[] args) {
int[][] testNumbers = {
{10, 2640},
{15, 13160},
{20, 41230},
{50, 1582700}
};

for (int[] testNumber : testNumbers) {
assert solution1(testNumber[0]) == testNumber[1]
&& solutions2(testNumber[0]) == testNumber[1];
}
}

private static int solution1(int n) {
int sum1 = 0;
int sum2 = 0;
for (int i = 1; i <= n; ++i) {
sum1 += i * i;
sum2 += i;
}
return sum2 * sum2 - sum1;
}


private static int solutions2(int n) {
int sumOfSquares = n * (n + 1) * (2 * n + 1) / 6;
int squareOfSum = (int) Math.pow((n * (n + 1) / 2.0), 2);
return squareOfSum - sumOfSquares;
}
}