diff --git a/src/n0008_string_to_integer_atoi.rs b/src/n0008_string_to_integer_atoi.rs
index cabb68bb..5eef8f01 100644
--- a/src/n0008_string_to_integer_atoi.rs
+++ b/src/n0008_string_to_integer_atoi.rs
@@ -74,7 +74,7 @@ impl Solution {
             if !num_matched {
                 match ch {
                     ' ' => {},
-                    '0'...'9' => {
+                    '0'..='9' => {
                         num_matched = true;
                         result = result * 10 + ch.to_digit(10).unwrap() as i64;
                     },
@@ -84,7 +84,7 @@ impl Solution {
                 }
             } else {
                 match ch {
-                    '0'...'9' => {
+                    '0'..='9' => {
                         result = result * 10 + ch.to_digit(10).unwrap() as i64;
                         if result > i32_max { break }
                     },
diff --git a/src/n0224_basic_calculator.rs b/src/n0224_basic_calculator.rs
index e448a0ab..bbdb5077 100644
--- a/src/n0224_basic_calculator.rs
+++ b/src/n0224_basic_calculator.rs
@@ -52,7 +52,7 @@ impl Solution {
         let mut in_num = false;
         for ch in s.chars() {
             match ch {
-                '0'...'9' => {
+                '0'..='9' => {
                     in_num = true;
                     num = 10 * num + (ch as u8 - '0' as u8) as i64;
                 }
diff --git a/src/n0227_basic_calculator_ii.rs b/src/n0227_basic_calculator_ii.rs
index 06fb2e5b..0b91565d 100644
--- a/src/n0227_basic_calculator_ii.rs
+++ b/src/n0227_basic_calculator_ii.rs
@@ -47,7 +47,7 @@ impl Solution {
         let mut multiple = true;
         for ch in s.chars() {
             match ch {
-                '0'...'9' => { curr = 10 * curr + (ch as u8 - '0' as u8) as i64; },
+                '0'..='9' => { curr = 10 * curr + (ch as u8 - '0' as u8) as i64; },
                 '+' | '-' => {
                     if has_prev {
                         if multiple {