12.整数转罗马数字

链接：12.整数转罗马数字
难度：Medium
标签：哈希表、数学、字符串
简介：给定一个整数，将其转为罗马数字。输入确保在 1 到 3999 的范围内。

题解 1 - typescript

• 编辑时间：2020-06-02
• 执行用时：144ms
• 内存消耗：41.3MB
• 编程语言：typescript
• 解法介绍：递归判断每一位。

function intToRoman(num: number): string {
  const len = (num + '').length;
  let s = '';
  switch (len) {
    case 4: {
      const n = ~~(num / 1000);
      for (let i = 0; i < n; i++) s += 'M';
      s += intToRoman(num % 1000);
      break;
    }
    case 3: {
      const n = ~~(num / 100);
      switch (n) {
        case 9: {
          s += 'CM';
          break;
        }
        case 8: {
          s += 'DCCC';
          break;
        }
        case 7: {
          s += 'DCC';
          break;
        }
        case 6: {
          s += 'DC';
          break;
        }
        case 5: {
          s += 'D';
          break;
        }
        case 4: {
          s += 'CD';
          break;
        }
        case 3: {
          s += 'CCC';
          break;
        }
        case 2: {
          s += 'CC';
          break;
        }
        case 1: {
          s += 'C';
          break;
        }
      }
      s += intToRoman(num % 100);
      break;
    }
    case 2: {
      const n = ~~(num / 10);
      switch (n) {
        case 9: {
          s += 'XC';
          break;
        }
        case 8: {
          s += 'LXXX';
          break;
        }
        case 7: {
          s += 'LXX';
          break;
        }
        case 6: {
          s += 'LX';
          break;
        }
        case 5: {
          s += 'L';
          break;
        }
        case 4: {
          s += 'XL';
          break;
        }
        case 3: {
          s += 'XXX';
          break;
        }
        case 2: {
          s += 'XX';
          break;
        }
        case 1: {
          s += 'X';
          break;
        }
      }
      s += intToRoman(num % 10);
      break;
    }
    case 1: {
      switch (num) {
        case 9: {
          s += 'IX';
          break;
        }
        case 8: {
          s += 'VIII';
          break;
        }
        case 7: {
          s += 'VII';
          break;
        }
        case 6: {
          s += 'VI';
          break;
        }
        case 5: {
          s += 'V';
          break;
        }
        case 4: {
          s += 'IV';
          break;
        }
        case 3: {
          s += 'III';
          break;
        }
        case 2: {
          s += 'II';
          break;
        }
        case 1: {
          s += 'I';
          break;
        }
      }
      break;
    }
  }
  return s;
}

题解 2 - typescript

• 编辑时间：2021-05-14
• 执行用时：212ms
• 内存消耗：44.3MB
• 编程语言：typescript
• 解法介绍：分节处理。

const config: Map<number, Map<number, string>> = new Map([
  [
    100,
    new Map([
      [1, 'C'],
      [5, 'D'],
      [10, 'M'],
    ]),
  ],
  [
    10,
    new Map([
      [1, 'X'],
      [5, 'L'],
      [10, 'C'],
    ]),
  ],
  [
    1,
    new Map([
      [1, 'I'],
      [5, 'V'],
      [10, 'X'],
    ]),
  ],
]);
function intToRoman(num: number): string {
  let ans = '';
  if (num >= 1000) {
    ans += 'M'.repeat(~~(num / 1000));
    num = num % 1000;
  }
  for (const [val, map] of config) {
    if (num < val) continue;
    const c1 = map.get(1)!;
    const c5 = map.get(5)!;
    const c10 = map.get(10)!;
    const c = ~~(num / val);
    num = num % val;
    if (c === 9) ans += c1 + c10;
    else if (c >= 5) ans += c5 + c1.repeat(c - 5);
    else if (c === 4) ans += c1 + c5;
    else ans += c1.repeat(c);
  }
  return ans;
}

题解 3 - typescript

• 编辑时间：2021-10-16
• 执行用时：148ms
• 内存消耗：44.2MB
• 编程语言：typescript
• 解法介绍：模拟。

function intToRoman(num: number): string {
  let ans = '';
  const list: { val: number; template: [string, string, string] }[] = [
    {
      val: 1000,
      template: ['M', 'M', 'M'],
    },
    {
      val: 100,
      template: ['M', 'D', 'C'],
    },
    {
      val: 10,
      template: ['C', 'L', 'X'],
    },
    {
      val: 1,
      template: ['X', 'V', 'I'],
    },
  ];
  for (const { val, template } of list) {
    if (num >= val) {
      ans += createStr(Math.floor(num / val), ...template);
      num %= val;
    }
  }
  return ans;
  function createStr(num: number, hight: string, mid: string, low: string) {
    if (num <= 3) return low.repeat(num);
    else if (num <= 5) return low.repeat(5 - num) + mid;
    else if (num <= 8) return mid + low.repeat(num - 5);
    else return low + hight;
  }
}