Solve #7 in Go.

007/10001st-prime.go

@@ -0,0 +1,36 @@
+package main
+
+import "fmt"
+
+func iSqrt(n int64) int64 {
+	var r1, r int64 = n, n + 1
+	for r1 < r {
+		r, r1 = r1, (r1+n/r1)>>1
+	}
+	return r
+}
+
+func PrimeSieve(n int64) []int64 {
+	result := make([]int64, 0, n)
+	sieve := make([]bool, n+1)
+	sn := iSqrt(n)
+	var i, j int64
+	for i = 2; i <= sn; i++ {
+		if !sieve[i] {
+			for j = i * i; j <= n; j += i {
+				sieve[j] = true
+			}
+		}
+	}
+	for i = 2; i <= n; i++ {
+		if !sieve[i] {
+			result = append(result, i)
+		}
+	}
+	return result
+}
+
+func main() {
+	primes := PrimeSieve(1000000)
+	fmt.Println(primes[10000])
+}