leetcode: Add 0012

src/leetcode/0012.integer-to-roman/Cargo.toml

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+[package]
+name = "lc-0012-integer-to-roman"
+version = "0.1.0"
+edition = "2021"
+publish = false
+
+[dependencies]

src/leetcode/0012.integer-to-roman/index.md

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+
+# 
+
+[问题描述](../problems/)

src/leetcode/0012.integer-to-roman/src/main.rs

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+// Copyright (c) 2024 Xu Shaohua <[email protected]>. All rights reserved.
+// Use of this source is governed by General Public License that can be found
+// in the LICENSE file.
+
+#[must_use]
+#[inline]
+pub const fn get_more_roman_symbols(num: i32) -> &'static str {
+    match num {
+        3000 => "MMM",
+        2000 => "MM",
+        1000 => "M",
+        900 => "CM",
+        800 => "DCCC",
+        700 => "DCC",
+        600 => "DC",
+        500 => "D",
+        400 => "CD",
+        300 => "CCC",
+        200 => "CC",
+        100 => "C",
+        90 => "XC",
+        80 => "LXXX",
+        70 => "LXX",
+        60 => "LX",
+        50 => "L",
+        40 => "XL",
+        30 => "XXX",
+        20 => "XX",
+        10 => "X",
+        9 => "IX",
+        8 => "VIII",
+        7 => "VII",
+        6 => "VI",
+        5 => "V",
+        4 => "IV",
+        3 => "III",
+        2 => "II",
+        1 => "I",
+        _ => "-",
+    }
+}
+
+// 模式匹配
+pub fn int_to_roman1(num: i32) -> String {
+    assert!((0..=3999).contains(&num));
+
+    let mut num = num;
+    let mut quot;
+    // 最大支持1000级的
+    let mut factor = 1000;
+    let mut out = String::new();
+
+    while num > 0 || factor > 0 {
+        // 计算商
+        quot = num / factor;
+        // 构造这个位的数值.
+        let val = quot * factor;
+
+        if val > 0 {
+            // 根据数值, 拿到对应的字符串
+            out += get_more_roman_symbols(val);
+        }
+
+        // 计算余数, 准备下一次循环使用
+        num %= factor;
+        factor /= 10;
+    }
+
+    out
+}
+
+#[must_use]
+#[inline]
+pub const fn get_roman_symbol(num: i32) -> char {
+    match num {
+        1000 => 'M',
+        500 => 'D',
+        100 => 'C',
+        50 => 'L',
+        10 => 'X',
+        5 => 'V',
+        1 => 'I',
+        _ => '-',
+    }
+}
+
+#[must_use]
+pub fn get_roman_symbols_manual(quot: i32, factor: i32) -> String {
+    match quot {
+        0 => String::new(),
+        val @ 1..=3 => {
+            let one = get_roman_symbol(factor);
+            let mut s = String::new();
+            // [one]
+            // [one, one]
+            // [one, one, one]
+            for _i in 0..val {
+                s.push(one);
+            }
+            s
+        }
+        4 => {
+            let five = get_roman_symbol(5 * factor);
+            let one = get_roman_symbol(factor);
+            let mut s = String::new();
+            // [one, five]
+            s.push(one);
+            s.push(five);
+            s
+        }
+        5 => get_roman_symbol(5 * factor).to_string(),
+        val @ 6..=8 => {
+            let five = get_roman_symbol(5 * factor);
+            let one = get_roman_symbol(factor);
+            let mut s = String::new();
+            // [five, one]
+            // [five, one, one]
+            // [five, one, one, one]
+            s.push(five);
+            for _i in 0..(val - 5) {
+                s.push(one);
+            }
+            s
+        }
+        9 => {
+            let ten = get_roman_symbol(10 * factor);
+            let one = get_roman_symbol(factor);
+            let mut s = String::new();
+            // [one, ten]
+            s.push(one);
+            s.push(ten);
+            s
+        }
+        _ => unimplemented!(),
+    }
+}
+
+// 部分模式匹配
+// 剩下的手动计算, 性能较差
+pub fn int_to_roman2(num: i32) -> String {
+    assert!((0..=3999).contains(&num));
+
+    let mut num = num;
+    let mut quot;
+    // 最大支持1000级的
+    let mut factor = 1000;
+    let mut out = String::new();
+
+    while num > 0 || factor > 0 {
+        // 计算商
+        quot = num / factor;
+
+        if quot > 0 {
+            // 构造这个位的数值对应的罗马数字.
+            out += &get_roman_symbols_manual(quot, factor);
+        }
+
+        // 计算余数, 准备下一次循环使用
+        num %= factor;
+        factor /= 10;
+    }
+
+    out
+}
+
+pub type SolutionFn = fn(i32) -> String;
+
+fn check_solution(func: SolutionFn) {
+    const RECORDS: &[(i32, &str)] = &[(3, "III"), (58, "LVIII"), (1994, "MCMXCIV"), (9, "IX")];
+    for record in RECORDS {
+        assert_eq!(func(record.0).as_str(), record.1);
+    }
+}
+
+fn main() {
+    check_solution(int_to_roman1);
+    check_solution(int_to_roman2);
+}
+
+#[cfg(test)]
+mod tests {
+    use super::{check_solution, int_to_roman1, int_to_roman2};
+
+    #[test]
+    fn test_solution1() {
+        check_solution(int_to_roman1);
+    }
+
+    #[test]
+    fn test_solution2() {
+        check_solution(int_to_roman2);
+    }
+}