add LC2 skeleton files for 7 ACM I/O patterns

LC2/7.go

@@ -0,0 +1,28 @@
+//go:build ignore
+
+// 读取不定长行：读入一行空格分隔的整数，输出它们的和
+// 输入示例：1 2 3 4 5
+// 输出示例：15
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+	"strconv"
+	"strings"
+)
+
+func main() {
+	scanner := bufio.NewScanner(os.Stdin)
+	scanner.Scan()
+	line := scanner.Text()
+
+	parts := strings.Fields(line)
+	sum := 0
+	for _, s := range parts {
+		n, _ := strconv.Atoi(s)
+		sum += n
+	}
+	fmt.Println(sum)
+}