add initial data

0007-reverse-integer/Cargo.lock

@@ -0,0 +1,7 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 4
+
+[[package]]
+name = "leetcode"
+version = "0.1.0"

0007-reverse-integer/Cargo.toml

@@ -0,0 +1,6 @@
+[package]
+name = "leetcode"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]

0007-reverse-integer/src/main.rs

@@ -0,0 +1,43 @@
+fn main() {
+    println!("Hello, world!");
+}
+
+fn try_reverse(x: i32) -> Option<i32> {
+    let mut i = x;
+    let mut result: i32 = 0;
+
+    while i != 0 {
+        let digit = i % 10;
+        result = result.checked_mul(10)?.checked_add(digit)?;
+
+        i /= 10;
+    }
+
+    Some(result)
+}
+
+pub fn reverse(x: i32) -> i32 {
+    try_reverse(x).unwrap_or(0)
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::reverse;
+
+    #[test]
+    fn test_1() {
+        assert_eq!(reverse(123), 321);
+    }
+    #[test]
+    fn test_2() {
+        assert_eq!(reverse(-123), -321);
+    }
+    #[test]
+    fn test_3() {
+        assert_eq!(reverse(120), 21);
+    }
+    #[test]
+    fn test_4() {
+        assert_eq!(reverse(1534236469), 0);
+    }
+}