leetcode: solve problem 13

leetcode/0013-roman-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 = "roman-to-integer"
+version = "0.1.0"

leetcode/0013-roman-to-integer/Cargo.toml

@@ -0,0 +1,8 @@
+[package]
+name = "roman-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]

leetcode/0013-roman-to-integer/src/lib.rs

@@ -0,0 +1,114 @@
+pub fn roman_to_int(s: String) -> i32 {
+    let mut res = 0;
+
+    let v: Vec<char> = s.chars().collect();
+    let mut check_prev = true;
+
+    for (i, ch) in v.iter().enumerate() {
+        let prev = if i > 0 { v[i - 1] } else { '0' };
+
+        match prev {
+            'I' => match *ch {
+                'V' => {
+                    res += 4;
+                    check_prev = false;
+                    continue;
+                }
+                'X' => {
+                    res += 9;
+                    check_prev = false;
+                    continue;
+                }
+                _ => (),
+            },
+            'X' => match *ch {
+                'L' => {
+                    res += 40;
+                    check_prev = false;
+                    continue;
+                }
+                'C' => {
+                    res += 90;
+                    check_prev = false;
+                    continue;
+                }
+                _ => {}
+            },
+            'C' => match *ch {
+                'D' => {
+                    res += 400;
+                    check_prev = false;
+                    continue;
+                }
+                'M' => {
+                    res += 900;
+                    check_prev = false;
+                    continue;
+                }
+                _ => {}
+            },
+            _ => (),
+        }
+
+        if check_prev && (prev == 'I' || prev == 'X' || prev == 'C') {
+            res += char_to_int(prev);
+        }
+
+        check_prev = true;
+
+        if *ch != 'I' && *ch != 'X' && *ch != 'C' {
+            res += char_to_int(*ch);
+        }
+    }
+
+    if check_prev {
+        let l = v[v.len() - 1];
+        if l == 'I' || l == 'X' || l == 'C' {
+            res += char_to_int(l);
+        }
+    }
+
+    res
+}
+
+fn char_to_int(c: char) -> i32 {
+    match c {
+        'I' => 1,
+        'V' => 5,
+        'X' => 10,
+        'L' => 50,
+        'C' => 100,
+        'D' => 500,
+        'M' => 1000,
+        _ => 0,
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::roman_to_int;
+
+    #[test]
+    fn simple_test() {
+        let result = roman_to_int("III".to_string());
+        assert_eq!(result, 3);
+    }
+
+    #[test]
+    fn advanced_test() {
+        let result = roman_to_int("LVIII".to_string());
+        assert_eq!(result, 58);
+    }
+
+    #[test]
+    fn sub() {
+        let result = roman_to_int("MCMXCIV".to_string());
+        assert_eq!(result, 1994);
+    }
+
+    #[test]
+    fn simple_sub() {
+        let result = roman_to_int("IX".to_string());
+        assert_eq!(result, 9);
+    }
+}