Integer to Roman LeetCode solution in C++

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class Solution {
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 public:
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  string intToRoman(int num) {
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    string ans = "";
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    while (num >= 1000) {
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      ans += 'M';
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      num -= 1000;
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    }
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    while (num >= 900) {
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      ans += "CM";
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      num -= 900;
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    }
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    while (num >= 500) {
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      ans += 'D';
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      num -= 500;
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    }
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    while (num >= 400) {
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      ans += "CD";
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      num -= 400;
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    }
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    while (num >= 100) {
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      ans += 'C';
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      num -= 100;
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    }
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    while (num >= 90) {
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      ans += "XC";
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      num -= 90;
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    }
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    while (num >= 50) {
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      ans += 'L';
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      num -= 50;
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    }
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    while (num >= 40) {
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      ans += "XL";
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      num -= 40;
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    }
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    while (num >= 10) {
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      ans += 'X';
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      num -= 10;
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    }
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    while (num >= 9) {
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      ans += "IX";
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      num -= 9;
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    }
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    while (num >= 5) {
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      ans += 'V';
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      num -= 5;
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    }
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    while (num >= 4) {
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      ans += "IV";
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      num -= 4;
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    }
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    while (num > 0) {
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      ans += 'I';
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      num -= 1;
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    }
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    return ans;
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  }
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};