Algorithms: Roman to Integer

Author: maxvoronov

README.md

@@ -1,6 +1,6 @@
 # LeetCode
 
-![Problems Solved](https://img.shields.io/badge/Problems%20Solved-13%20%2F%202046-1f425f?logo=leetcode) 
+![Problems Solved](https://img.shields.io/badge/Problems%20Solved-14%20%2F%202046-1f425f?logo=leetcode) 
 ![Language: Golang](https://img.shields.io/badge/language-Golang-00ADD8?logo=go) 
 
 ### LeetCode Algorithm
@@ -11,6 +11,7 @@
 | 2   | [Add Two Numbers](https://leetcode.com/problems/add-two-numbers/) | [Go](go/0002_add_two_numbers) | 🟡 |
 | 7   | [Reverse Integer](https://leetcode.com/problems/reverse-integer/) | [Go](go/0007_reverse_integer) | 🟡 |
 | 9   | [Palindrome Number](https://leetcode.com/problems/palindrome-number/) | [Go](go/0009_palindrome_number) | 🟢 |
+| 13  | [Roman to Integer](https://leetcode.com/problems/roman-to-integer/) | [Go](go/0013_roman_to_integer) | 🟢 |
 | 17  | [Letter Combinations of a Phone Number](https://leetcode.com/problems/letter-combinations-of-a-phone-number/) | [Go](go/0017_letter_combinations_phone) | 🟡 |
 | 20  | [Valid Parentheses](https://leetcode.com/problems/valid-parentheses/) | [Go](go/0020_valid_parentheses) | 🟢 |
 | 35  | [Search Insert Position](https://leetcode.com/problems/search-insert-position/) | [Go](go/0035_search_insert_position) | 🟢 |

go/0013_roman_to_integer/solution.go

@@ -0,0 +1,28 @@
+package roman_to_integer
+
+var numsMap = map[byte]int{
+	'I': 1,
+	'V': 5,
+	'X': 10,
+	'L': 50,
+	'C': 100,
+	'D': 500,
+	'M': 1000,
+}
+
+func romanToInt(s string) int {
+	result, sLen := 0, len(s)
+	for i := 0; i < sLen; i++ {
+		num := numsMap[s[i]]
+		if i > 0 {
+			prevNum := numsMap[s[i-1]]
+			if prevNum < num && (num/prevNum == 5 || num/prevNum == 10) {
+				result += num - prevNum - prevNum
+				continue
+			}
+		}
+		result += num
+	}
+
+	return result
+}

go/0013_roman_to_integer/solution_test.go

@@ -0,0 +1,27 @@
+package roman_to_integer
+
+import "testing"
+
+func Test_romanToInt(t *testing.T) {
+	tests := []struct {
+		input string
+		want  int
+	}{
+		{input: "I", want: 1},
+		{input: "III", want: 3},
+		{input: "IV", want: 4},
+		{input: "VI", want: 6},
+		{input: "IX", want: 9},
+		{input: "LVIII", want: 58},
+		{input: "MCMXCIV", want: 1994},
+		{input: "MMMCMXCIX", want: 3999},
+		{input: "MMMCCCXXXIII", want: 3333},
+	}
+
+	for i, tc := range tests {
+		got := romanToInt(tc.input)
+		if tc.want != got {
+			t.Fatalf("Case #%d: expected: %v, got: %v", i+1, tc.want, got)
+		}
+	}
+}