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13. Roman to Integer #28

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zwfang merged 1 commit into master from roman-to-integer
Dec 31, 2018
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1 change: 1 addition & 0 deletions README.md
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Original file line number Diff line number Diff line change
Expand Up @@ -88,6 +88,7 @@ continually updating 😃.
### Math
* [7. Reverse Integer](src/0007_reverse_integer/reverse_integer.go)
* [9. Palindrome Number](src/0009_palindrome_number/palindrome_number.go)
* [13. Roman to Integer](src/0013_roman_to_integer/roman_to_integer.go)   *`string`*

<details>
</details>
29 changes: 29 additions & 0 deletions src/0013_roman_to_integer/roman_to_integer.go
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/*
13. Roman to Integer
https://leetcode.com/problems/roman-to-integer/
*/
// time: 2018年12月31日

package rti

// time complexity: O(n)
// space complexity: O(1)
func romanToInt(s string) int {
if 0 == len(s) {
return 0
}

digits := map[byte]int{'I': 1, 'V': 5, 'X': 10, 'L': 50, 'C': 100, 'D': 500, 'M': 1000}
sum := digits[s[len(s)-1]]

for i := len(s) - 1; i > 0; i-- {
cur := digits[s[i]]
pre := digits[s[i-1]]
if cur > pre {
sum -= pre
} else {
sum += pre
}
}
return sum
}
21 changes: 21 additions & 0 deletions src/0013_roman_to_integer/roman_to_integer_test.go
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package rti

import "testing"

func TestRomanToInt(t *testing.T) {
testCases := []string{
"III",
"IV",
"IX",
"LVIII",
"MCMXCIV",
"",
}
expected := []int{3, 4, 9, 58, 1994, 0}

for index, s := range testCases {
if res := romanToInt(s); res != expected[index] {
t.Errorf("expected %d, got %d", expected[index], res)
}
}
}
1 change: 1 addition & 0 deletions src/README.md
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Expand Up @@ -9,6 +9,7 @@
|0007|[7. Reverse Integer](0007_reverse_integer/reverse_integer.go)|Easy|*`math`*|
|0009|[9. Palindrome Number](0009_palindrome_number/palindrome_number.go)|Easy|*`math`*|
|0011|[11. Container With Most Water](0011_container_with_most_water/container_with_most_water.go)|Medium|*`array;`* *`double index`*|
|0013|[13. Roman to Integer](0013_roman_to_integer/roman_to_integer.go)|Easy|*`math`*|
|0017|[Letter Combinations of a Phone Number](0017_letter_combination_of_a_phone_number/letter_combination_of_phone_number.go)|Medium|*`tree`*|
|0020|[Valid Parentheses](0020_valid_parentheses/valid_parentheses.go)|Easy|*`string;`* *`stack`*|
|0021|[Merge Two Sorted Lists](0021_merge_two_sorted_lists/mergeTwoLists.go)|Easy|*`linked list`*|
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