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1021. Remove Outermost Parentheses #86

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zwfang merged 1 commit into master from 1021
May 5, 2020
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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 @@ -63,6 +63,7 @@ continually updating 😃.
* [345. Reverse Vowels of a String](src/0345_reverse_vowels_of_a_string/reverse_vowels.go)   *`string;`*  *`double index`*
* [438. Find All Anagrams in a String](src/0438_all_anagrams_in_a_string/all_anagrams_in_a_string.go)   *`sliding window`*
* [557. Reverse Words in a String III](src/0557_reverse_words_in_a_string_3/reverse_words_in_a_string_3.go)
* [1021. Remove Outermost Parentheses](src/1021_Remove_Outermost_Parentheses/remove_outmost_parentheses.go)   *`stack`*

### Linked List
* [2. Add Two Numbers](src/0002_add_two_numbers/add_two_numbers.go)   *`recursion;`*  *`math`*
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/*
1021. Remove Outermost Parentheses

A valid parentheses string is either empty (""), "(" + A + ")", or A + B, where A and B are valid parentheses strings, and + represents string concatenation. For example, "", "()", "(())()", and "(()(()))" are all valid parentheses strings.

A valid parentheses string S is primitive if it is nonempty, and there does not exist a way to split it into S = A+B, with A and B nonempty valid parentheses strings.

Given a valid parentheses string S, consider its primitive decomposition: S = P_1 + P_2 + ... + P_k, where P_i are primitive valid parentheses strings.

Return S after removing the outermost parentheses of every primitive string in the primitive decomposition of S.



Example 1:

Input: "(()())(())"
Output: "()()()"
Explanation:
The input string is "(()())(())", with primitive decomposition "(()())" + "(())".
After removing outer parentheses of each part, this is "()()" + "()" = "()()()".
Example 2:

Input: "(()())(())(()(()))"
Output: "()()()()(())"
Explanation:
The input string is "(()())(())(()(()))", with primitive decomposition "(()())" + "(())" + "(()(()))".
After removing outer parentheses of each part, this is "()()" + "()" + "()(())" = "()()()()(())".
Example 3:

Input: "()()"
Output: ""
Explanation:
The input string is "()()", with primitive decomposition "()" + "()".
After removing outer parentheses of each part, this is "" + "" = "".


Note:

S.length <= 10000
S[i] is "(" or ")"
S is a valid parentheses string



*/

// time: 2020年05月04日

package removeoutmostparentheses

// time complexity: O(n), where n is length of S.
// space complexity: O(1)
func removeOuterParentheses(S string) string {
// S is valid parentheses string, so, s is empty "" or starts with "("
if len(S) == 0 {
return S
}

var stackLength, left int

var ret string

for i := 0; i < len(S); i++ {
if stackLength == 0 {
left = i
}
if S[i] == '(' {
stackLength++
} else {
stackLength--
}
if stackLength == 0 {
ret += S[left+1 : i]
}
}
return ret
}
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package removeoutmostparentheses

import (
"testing"
)

func TestRemoveOuterParentheses(t *testing.T) {
testCases := []map[string]string{
{"case": "(()())(())", "expected": "()()()"},
{"case": "(()())(())(()(()))", "expected": "()()()()(())"},
{"case": "", "expected": ""},
{"case": "()()", "expected": ""},
}

for _, testCase := range testCases {
if testCase["expected"] != removeOuterParentheses(testCase["case"]) {
t.Errorf("hello")
}
}
}
3 changes: 2 additions & 1 deletion src/README.md
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Expand Up @@ -114,4 +114,5 @@
|0728|[Self Dividing Numbers](./0728_self_dividing_numbers/self_dividing_numbers.go)|Easy||
|0735|[735. Asteroid Collision](0735_asteroid_collision/ac.go)|Medium|*`stack`*|
|0747|[Largest Number At Least Twice of Others](./0747_largest_number_at_least_twice_of_others/largest_number_at_least_twice_of_others.go)|Easy||
|0872|[872. Leaf-Similar Trees](0872_leaf_similar_trees/leaf_similar_trees.go)|Easy|*`binary tree`*|
|0872|[872. Leaf-Similar Trees](0872_leaf_similar_trees/leaf_similar_trees.go)|Easy|*`binary tree`*|
|1021|[1021. Remove Outermost Parentheses](1021_Remove_Outermost_Parentheses/remove_outmost_parentheses.go)|Easy|*`stack`*|

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