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[Golang] Summation of Primes - Problem 10 - Project Euler
source link: http://siongui.github.io/2017/06/09/go-summation-of-primes-problem-10-project-euler/
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[Golang] Summation of Primes - Problem 10 - Project Euler
June 09, 2017
Go solution to summation of primes - Problem 10 - Project Euler. [1]
Problem:
The sum of the primes below 10 is 2 + 3 + 5 + 7 = 17.
Find the sum of all the primes below two million.
Solution:
142913828922
We use sieve of Eratosthenes [2] to find out all prime number under 2,000,000. Note that we cannot use int type because of integer overflow [3]. Use int64 type instead.
package main import ( "fmt" ) func SieveOfEratosthenes(n int64) []int64 { // Create a boolean array "prime[0..n]" and initialize // all entries it as true. A value in prime[i] will // finally be false if i is Not a prime, else true. integers := make([]bool, n+1) for i := int64(2); i < n+1; i++ { integers[i] = true } for p := int64(2); p*p <= n; p++ { // If integers[p] is not changed, then it is a prime if integers[p] == true { // Update all multiples of p for i := p * 2; i <= n; i += p { integers[i] = false } } } // return all prime numbers <= n var primes []int64 for p := int64(2); p <= n; p++ { if integers[p] == true { primes = append(primes, p) } } return primes } func main() { primes := SieveOfEratosthenes(2000000) fmt.Println(len(primes)) sum := int64(0) for _, prime := range primes { sum1 := sum + prime if sum1 < sum { fmt.Println(sum) } else { sum = sum1 } } fmt.Println(sum) }
Tested on: Go Playground
References:
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