20210608-13.Roman to integer solution

chobobdev/13/13.go

@@ -0,0 +1,79 @@
+// 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].
+
+var roman = map[string]int{
+	"I": 1,
+	"V": 5,
+	"X": 10,
+	"L": 50,
+	"C": 100,
+	"D": 500,
+	"M": 1000,
+}
+
+func romanToInt(s string) int {
+	if len(s) == 0 {
+		return 0
+	}
+	currentnum, prevint, total := 0, 0, 0
+	for i := 0; i < len(s); i++ {
+		char := s[len(s)-(i+1) : len(s)-i]
+		currentnum = roman[char]
+		if currentnum < prevint {
+			total = total - currentnum
+		} else {
+			total = total + currentnum
+		}
+		prevint = currentnum
+	}
+	return total
+
+}
+
+// Runtime: 12 ms, faster than 31.15% of Go online submissions for Roman to Integer.
+// Memory Usage: 3.3 MB, less than 19.78% of Go online submissions for Roman to Integer.

chobobdev/README.md

@@ -21,12 +21,13 @@ Go lang을 활용해 많은 알고리즘 해결
 | # | 시도 날짜  | 문제 이름 | 언어 |            링크             |
 | :--: | :--------: | :-------: | :--: |:--------------------------: |
 | 1 | 2021-05-20 | 27. Remove Element| Go |[:link:](27.go) |
-| 2 | 2021-05-23 | 58 . Length of the last word | Go |[:link:](58.md)|
-| 3 | 2021-05-24 | 7. Reverse Integer | Go,JS |[:link:](7.md)|
-| 5 | 2021-05-20 | 26.Remove Duplicates from Sorted Array| Go |[:link:](26.md) |
-| 6 | 2021-05-29 | 9. Palindrome Number | Go | [:link:](9.md) |
-| 7 | 2021-05-31 |69. Sqrt(x) | Go | [:link:](69.md) |
-| 8 | 2021-05-31 |796. Rotate String | Go | [:link:](796.md) |
+| 2 | 2021-05-23 | 58 . Length of the last word | Go |[:link:](58.go)|
+| 3 | 2021-05-24 | 7. Reverse Integer | Go,JS |[:link:](7.go)|
+| 5 | 2021-05-20 | 26.Remove Duplicates from Sorted Array| Go |[:link:](26.go) |
+| 6 | 2021-05-29 | 9. Palindrome Number | Go | [:link:](9.go) |
+| 7 | 2021-05-31 |69. Sqrt(x) | Go | [:link:](69.go) |
+| 8 | 2021-05-31 |796. Rotate String | Go | [:link:](796.go) |
+| 9 | 2021-06-08 | 13. Roman to Integer | Go | [:link:](13.go) |
 
 
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