41: pandigital prime

41_pandigital_prime/main.go

@@ -0,0 +1,49 @@
+package main
+
+import (
+	"fmt"
+	"strconv"
+	"strings"
+)
+
+func main() {
+	for i := 987654321; i > 1; i-- {
+		if !isPandigital(strconv.Itoa(i)) {
+			continue
+		}
+		fmt.Println(i)
+		if isPrime(i) {
+			fmt.Println("largest pandigital prime:", i)
+			break
+		}
+	}
+}
+
+func isPrime(n int) bool {
+	if n <= 1 {
+		return false
+	}
+	res := n
+	//牛顿法求平方根
+	for res*res > n {
+		res = (res + n/res) / 2
+	}
+	divider := 2
+	for divider <= res {
+		if n%divider == 0 {
+			return false
+		}
+		divider++
+	}
+	return true
+}
+
+func isPandigital(s string) bool {
+	l := len(s)
+	for i := 1; i <= l; i++ {
+		if !strings.Contains(s, strconv.Itoa(i)) {
+			return false
+		}
+	}
+	return true
+}