Added tasks 12, 13, 14

Author: javadev

LeetCodeNet.Tests/G0001_0100/S0012_integer_to_roman/SolutionTest.cs

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+namespace LeetCodeNet.G0001_0100.S0012_integer_to_roman {
+
+using System;
+using Xunit;
+
+public class SolutionTest
+{
+    [Fact]
+    public void IntToRoman()
+    {
+        Assert.Equal("III", new Solution().IntToRoman(3));
+    }
+
+    [Fact]
+    public void IntToRoman2()
+    {
+        Assert.Equal("IV", new Solution().IntToRoman(4));
+    }
+
+    [Fact]
+    public void IntToRoman3()
+    {
+        Assert.Equal("IX", new Solution().IntToRoman(9));
+    }
+
+    [Fact]
+    public void IntToRoman4()
+    {
+        Assert.Equal("LVIII", new Solution().IntToRoman(58));
+    }
+
+    [Fact]
+    public void IntToRoman5()
+    {
+        Assert.Equal("MCMXCIV", new Solution().IntToRoman(1994));
+    }
+}
+}

LeetCodeNet.Tests/G0001_0100/S0013_roman_to_integer/SolutionTest.cs

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+namespace LeetCodeNet.G0001_0100.S0013_roman_to_integer {
+
+using System;
+using Xunit;
+
+public class SolutionTest
+{
+    [Fact]
+    public void RomanToInt()
+    {
+        Assert.Equal(3, new Solution().RomanToInt("III"));
+    }
+
+    [Fact]
+    public void RomanToInt2()
+    {
+        Assert.Equal(4, new Solution().RomanToInt("IV"));
+    }
+
+    [Fact]
+    public void RomanToInt3()
+    {
+        Assert.Equal(9, new Solution().RomanToInt("IX"));
+    }
+
+    [Fact]
+    public void RomanToInt4()
+    {
+        Assert.Equal(58, new Solution().RomanToInt("LVIII"));
+    }
+
+    [Fact]
+    public void RomanToInt5()
+    {
+        Assert.Equal(1994, new Solution().RomanToInt("MCMXCIV"));
+    }
+}
+}

LeetCodeNet.Tests/G0001_0100/S0014_longest_common_prefix/SolutionTest.cs

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+namespace LeetCodeNet.G0001_0100.S0014_longest_common_prefix {
+
+using System;
+using Xunit;
+
+public class SolutionTest
+{
+    [Fact]
+    public void LongestCommonPrefix()
+    {
+        Assert.Equal("fl", new Solution().LongestCommonPrefix(new string[] { "flower", "flow", "flight" }));
+    }
+
+    [Fact]
+    public void LongestCommonPrefix2()
+    {
+        Assert.Equal("", new Solution().LongestCommonPrefix(new string[] { "dog", "racecar", "car" }));
+    }
+}
+}

LeetCodeNet/G0001_0100/S0012_integer_to_roman/Solution.cs

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+namespace LeetCodeNet.G0001_0100.S0012_integer_to_roman {
+
+// #Medium #String #Hash_Table #Math #Top_Interview_150_Array/String
+// #2025_06_20_Time_2_ms_(87.59%)_Space_45.13_MB_(98.99%)
+
+public class Solution
+{
+    public string IntToRoman(int num)
+    {
+        var sb = new System.Text.StringBuilder();
+        int m = 1000;
+        int c = 100;
+        int x = 10;
+        int i = 1;
+        num = Numerals(sb, num, m, ' ', ' ', 'M');
+        num = Numerals(sb, num, c, 'M', 'D', 'C');
+        num = Numerals(sb, num, x, 'C', 'L', 'X');
+        Numerals(sb, num, i, 'X', 'V', 'I');
+        return sb.ToString();
+    }
+
+    private int Numerals(System.Text.StringBuilder sb, int num, int one, char cTen, char cFive, char cOne)
+    {
+        int div = num / one;
+        switch (div)
+        {
+            case 9:
+                sb.Append(cOne);
+                sb.Append(cTen);
+                break;
+            case 8:
+                sb.Append(cFive);
+                sb.Append(cOne);
+                sb.Append(cOne);
+                sb.Append(cOne);
+                break;
+            case 7:
+                sb.Append(cFive);
+                sb.Append(cOne);
+                sb.Append(cOne);
+                break;
+            case 6:
+                sb.Append(cFive);
+                sb.Append(cOne);
+                break;
+            case 5:
+                sb.Append(cFive);
+                break;
+            case 4:
+                sb.Append(cOne);
+                sb.Append(cFive);
+                break;
+            case 3:
+                sb.Append(cOne);
+                sb.Append(cOne);
+                sb.Append(cOne);
+                break;
+            case 2:
+                sb.Append(cOne);
+                sb.Append(cOne);
+                break;
+            case 1:
+                sb.Append(cOne);
+                break;
+            default:
+                break;
+        }
+        return num - (div * one);
+    }
+}
+}

LeetCodeNet/G0001_0100/S0012_integer_to_roman/readme.md

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+12\. Integer to Roman
+
+Medium
+
+Roman numerals are represented by seven different symbols: `I`, `V`, `X`, `L`, `C`, `D` and `M`.
+
+    Symbol   Value
+     I        1
+     V        5
+     X        10
+     L        50
+     C        100
+     D        500
+     M        1000
+
+For example, `2` is written as `II` in Roman numeral, just two one's added together. `12` is written as `XII`, which is simply `X + II`. The number `27` is written as `XXVII`, which is `XX + V + II`.
+
+Roman numerals are usually written largest to smallest from left to right. However, the numeral for four is not `IIII`. Instead, the number four is written as `IV`. Because the one is before the five we subtract it making four. The same principle applies to the number nine, which is written as `IX`. There are six instances where subtraction is used:
+
+*   `I` can be placed before `V` (5) and `X` (10) to make 4 and 9.
+*   `X` can be placed before `L` (50) and `C` (100) to make 40 and 90.
+*   `C` can be placed before `D` (500) and `M` (1000) to make 400 and 900.
+
+Given an integer, convert it to a roman numeral.
+
+**Example 1:**
+
+**Input:** num = 3
+
+**Output:** "III" 
+
+**Example 2:**
+
+**Input:** num = 4
+
+**Output:** "IV" 
+
+**Example 3:**
+
+**Input:** num = 9
+
+**Output:** "IX" 
+
+**Example 4:**
+
+**Input:** num = 58
+
+**Output:** "LVIII"
+
+**Explanation:** L = 50, V = 5, III = 3. 
+
+**Example 5:**
+
+**Input:** num = 1994
+
+**Output:** "MCMXCIV"
+
+**Explanation:** M = 1000, CM = 900, XC = 90 and IV = 4. 
+
+**Constraints:**
+
+*   `1 <= num <= 3999`

LeetCodeNet/G0001_0100/S0013_roman_to_integer/Solution.cs

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+namespace LeetCodeNet.G0001_0100.S0013_roman_to_integer {
+
+// #Easy #Top_100_Liked_Questions #Top_Interview_Questions #String #Hash_Table #Math
+// #Top_Interview_150_Array/String #2025_06_20_Time_1_ms_(99.81%)_Space_49.42_MB_(80.66%)
+
+public class Solution
+{
+    public int RomanToInt(string s)
+    {
+        int x = 0;
+        char y;
+        for (int i = 0; i < s.Length; i++)
+        {
+            y = s[i];
+            switch (y)
+            {
+                case 'I':
+                    x = GetX(s, x, i, 1, 'V', 'X');
+                    break;
+                case 'V':
+                    x += 5;
+                    break;
+                case 'X':
+                    x = GetX(s, x, i, 10, 'L', 'C');
+                    break;
+                case 'L':
+                    x += 50;
+                    break;
+                case 'C':
+                    x = GetX(s, x, i, 100, 'D', 'M');
+                    break;
+                case 'D':
+                    x += 500;
+                    break;
+                case 'M':
+                    x += 1000;
+                    break;
+                default:
+                    break;
+            }
+        }
+        return x;
+    }
+
+    private int GetX(string s, int x, int i, int i2, char v, char x2)
+    {
+        if (i + 1 == s.Length)
+        {
+            x += i2;
+        }
+        else if (s[i + 1] == v)
+        {
+            x -= i2;
+        }
+        else if (s[i + 1] == x2)
+        {
+            x -= i2;
+        }
+        else
+        {
+            x += i2;
+        }
+        return x;
+    }
+}
+}

LeetCodeNet/G0001_0100/S0013_roman_to_integer/readme.md

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+13\. Roman to Integer
+
+Easy
+
+Roman numerals are represented by seven different symbols: `I`, `V`, `X`, `L`, `C`, `D` and `M`.
+
+    Symbol  Value
+     I       1
+     V       5
+     X       10
+     L       50
+     C       100
+     D       500
+     M       1000
+
+For example, `2` is written as `II` in Roman numeral, just two one's added together. `12` is written as `XII`, which is simply `X + II`. The number `27` is written as `XXVII`, which is `XX + V + II`.
+
+Roman numerals are usually written largest to smallest from left to right. However, the numeral for four is not `IIII`. Instead, the number four is written as `IV`. Because the one is before the five we subtract it making four. The same principle applies to the number nine, which is written as `IX`. There are six instances where subtraction is used:
+
+*   `I` can be placed before `V` (5) and `X` (10) to make 4 and 9.
+*   `X` can be placed before `L` (50) and `C` (100) to make 40 and 90.
+*   `C` can be placed before `D` (500) and `M` (1000) to make 400 and 900.
+
+Given a roman numeral, convert it to an integer.
+
+**Example 1:**
+
+**Input:** s = "III"
+
+**Output:** 3 
+
+**Example 2:**
+
+**Input:** s = "IV"
+
+**Output:** 4 
+
+**Example 3:**
+
+**Input:** s = "IX"
+
+**Output:** 9 
+
+**Example 4:**
+
+**Input:** s = "LVIII"
+
+**Output:** 58
+
+**Explanation:** L = 50, V= 5, III = 3. 
+
+**Example 5:**
+
+**Input:** s = "MCMXCIV"
+
+**Output:** 1994
+
+**Explanation:** M = 1000, CM = 900, XC = 90 and IV = 4. 
+
+**Constraints:**
+
+*   `1 <= s.length <= 15`
+*   `s` contains only the characters `('I', 'V', 'X', 'L', 'C', 'D', 'M')`.
+*   It is **guaranteed** that `s` is a valid roman numeral in the range `[1, 3999]`.