Problem 8: string to integer

.gitignore

@@ -1,2 +1,3 @@
 *.o
 bin
+target

problems/8-string-to-integer/Cargo.lock

@@ -0,0 +1,7 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "string-to-integer"
+version = "0.1.0"

problems/8-string-to-integer/Cargo.toml

@@ -0,0 +1,8 @@
+[package]
+name = "string-to-integer"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

problems/8-string-to-integer/src/lib.rs

@@ -0,0 +1,148 @@
+use std::convert::TryInto;
+
+pub struct Solution{}
+
+impl Solution {
+    pub fn my_atoi(s: String) -> i32 {
+        let mut res: i32 = 0;
+        let mut sign: i32 = 1;
+        let mut sign_was_scanned = false;
+        let mut digit_was_scanned = false;
+
+        for c in s.chars() {
+            if c >= '0' && c <= '9' {
+                digit_was_scanned = true;
+                let conv: i32 = c.to_digit(10).unwrap().try_into().unwrap();
+                // Test overflow
+                if sign > 0 && res > (i32::MAX - conv * sign) / 10 {
+                    return i32::MAX;
+                }
+                if sign < 0 && res < (i32::MIN - conv * sign) / 10 {
+                    return i32::MIN;
+                }
+                // Add new digit
+                res = res * 10 + conv * sign;
+            }
+            // First '-'
+            else if c == '-' && sign_was_scanned == false && digit_was_scanned == false {
+                sign_was_scanned = true;
+                sign *= -1;
+            }
+            // Repeated '-' or '-' after number
+            else if c == '-' {
+                return res;
+            }
+            // First '+'
+            else if c == '+' && sign_was_scanned == false && digit_was_scanned == false {
+                sign_was_scanned = true;
+            }
+            // Repeated '+' or '+' after number
+            else if c == '+' {
+                return res;
+            }
+            // Letters before number
+            else if c != '+' && c != ' ' && digit_was_scanned == false {
+                return 0;
+            }
+            // Space after sign
+            else if c == ' ' && sign_was_scanned {
+                return res;
+            }
+            // Letters after number
+            else if digit_was_scanned == true {
+                return res;
+            }
+        }
+
+        return res;
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_simple_string() {
+        let input = String::from("42");
+        let result = Solution::my_atoi(input);
+        assert_eq!(result, 42);
+    }
+
+    #[test]
+    fn test_spaces() {
+        let input = String::from("   -42");
+        let result = Solution::my_atoi(input);
+        assert_eq!(result, -42);
+    }
+
+    #[test]
+    fn test_words() {
+        let input = String::from("4193 with words");
+        let result = Solution::my_atoi(input);
+        assert_eq!(result, 4193);
+    }
+
+    #[test]
+    fn test_zeros() {
+        let input = String::from("0032");
+        let result = Solution::my_atoi(input);
+        assert_eq!(result, 32);
+    }
+
+    #[test]
+    fn test_max_int() {
+        let input = String::from("21474242483648");
+        let result = Solution::my_atoi(input);
+        assert_eq!(result, i32::MAX);
+    }
+
+    #[test]
+    fn test_min_int() {
+        let input = String::from("-2424147483649");
+        let result = Solution::my_atoi(input);
+        assert_eq!(result, i32::MIN);
+    }
+
+    #[test]
+    fn test_invalid_string() {
+        let input = String::from("words and 987");
+        let result = Solution::my_atoi(input);
+        assert_eq!(result, 0);
+    }
+
+    #[test]
+    fn test_garbage_after_number() {
+        let input = String::from("3.14159");
+        let result = Solution::my_atoi(input);
+        assert_eq!(result, 3);
+    }
+
+    #[test]
+    fn test_multiple_signs() {
+        let input = String::from("+-12");
+        let result = Solution::my_atoi(input);
+        assert_eq!(result, 0);
+    }
+
+    #[test]
+    fn test_sign_after_number() {
+        let input = String::from("00000-42a1234");
+        let result = Solution::my_atoi(input);
+        assert_eq!(result, 0);
+    }
+
+    #[test]
+    fn test_minus_after_negative_number() {
+        let input = String::from("-5-");
+        let result = Solution::my_atoi(input);
+        assert_eq!(result, -5);
+    }
+
+    #[test]
+    fn test_space_after_sign() {
+        let input = String::from("  +  413");
+        let result = Solution::my_atoi(input);
+        assert_eq!(result, 0);
+    }
+}

readme.md

@@ -6,15 +6,26 @@
 
 For programs written in C:
 
-```
+```bash
 cd problems/random-problem
 make
 make run
 ```
 
+For programs written in Rust:
+
+```bash
+cd problems/random-problem
+cargo test
+```
+
 ## Solution structure
 
 For programs written in C:
 
 - `lib.c` - the solution itself
 - `main.c` - tests
+
+For programs written in Rust:
+
+- `src/lib.rs` - solution and tests