rename directory

13_large_sum/main.go

@@ -0,0 +1,40 @@
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"io"
+	"math/big"
+	"os"
+)
+
+func main() {
+	fi, err := os.Open("./digits.txt")
+	if err != nil {
+		panic(err)
+	}
+	defer fi.Close()
+
+	br := bufio.NewReader(fi)
+	var input []*big.Int
+	for {
+		a, _, e := br.ReadLine()
+		if e == io.EOF {
+			break
+		}
+		i, ok := (&big.Int{}).SetString(string(a), 0)
+		if !ok {
+			panic("invalid number")
+		}
+		input = append(input, i)
+	}
+
+	sum := &big.Int{}
+	for _, v := range input {
+		sum = sum.Add(sum, v)
+	}
+
+	fmt.Println(sum)
+
+	fmt.Println("ten digits is", sum.String()[:10])
+}