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15. 3Sum (#78)

* 15 solved. * fix bug * fix bug * fix bug

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`@@ -13,6 +13,7 @@ continually updating 😃.`
`13`	`13`	* [1. Two Sum](src/0001_two_sum/twosum.go)   `lookup table;`  `hash table`
`14`	`14`	* [4. Median of Two Sorted Arrays](src/0004_median_of_two_sorted_arrays/motsa.go)   `binary search;`  `divide and conquer`
`15`	`15`	* [11. Container With Most Water](src/0011_container_with_most_water/container_with_most_water.go)   `double index;`  `array`
	`16`	+* [15. 3Sum](src/0015_3Sum/3sum.go)   `double index;`  `array`
`16`	`17`	* [26. Remove Duplicates from Sorted Array](src/0026_remove_duplicates_from_sorted_array/rdfsa.go)   `double index;`  `array`
`17`	`18`	* [27. Remove Element](src/0027_remove_element/remove_element.go)   `double index;`  `array`
`18`	`19`	`* [48. Rotate Image](src/0048_rotate_image/rotate_image.go)`

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`@@ -0,0 +1,44 @@`
	`1`	`+/*`
	`2`	`+15. 3Sum`
	`3`	`+https://leetcode.com/problems/3sum/`
	`4`	`+*/`
	`5`	`+// time: 2019年03月01日`
	`6`	`+`
	`7`	`+package threesum`
	`8`	`+`
	`9`	`+import "sort"`
	`10`	`+`
	`11`	`+// time complexity: O(n^2)`
	`12`	`+func threeSum(nums []int) [][]int {`
	`13`	`+ sort.Ints(nums)`
	`14`	`+ var res [][]int`
	`15`	`+ for i := 0; i < len(nums)-2; i++ {`
	`16`	`+ if nums[i] > 0 {`
	`17`	`+ break`
	`18`	`+ }`
	`19`	`+ if i > 0 && nums[i] == nums[i-1] {`
	`20`	`+ continue`
	`21`	`+ }`
	`22`	`+ for l, r := i+1, len(nums)-1; l < r; {`
	`23`	`+ if l > i+1 && nums[l] == nums[l-1] {`
	`24`	`+ l++`
	`25`	`+ continue`
	`26`	`+ }`
	`27`	`+ if r < len(nums)-1 && nums[r] == nums[r+1] {`
	`28`	`+ r--`
	`29`	`+ continue`
	`30`	`+ }`
	`31`	`+ switch sum := nums[i] + nums[l] + nums[r]; {`
	`32`	`+ case sum < 0:`
	`33`	`+ l++`
	`34`	`+ case sum > 0:`
	`35`	`+ r--`
	`36`	`+ default:`
	`37`	`+ res = append(res, []int{nums[i], nums[l], nums[r]})`
	`38`	`+ l++`
	`39`	`+ r--`
	`40`	`+ }`
	`41`	`+ }`
	`42`	`+ }`
	`43`	`+ return res`
	`44`	`+}`

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`@@ -0,0 +1,23 @@`
	`1`	`+package threesum`
	`2`	`+`
	`3`	`+import (`
	`4`	`+ "reflect"`
	`5`	`+ "testing"`
	`6`	`+)`
	`7`	`+`
	`8`	`+func TestThreeSum(t *testing.T) {`
	`9`	`+ testData := [][]int{`
	`10`	`+ {-1, 0, 1, 2, -6, -4},`
	`11`	`+ {-7, 3, -7, 3, 4, 5, 6, 6, 4},`
	`12`	`+ }`
	`13`	`+ expected := [][][]int{`
	`14`	`+ {{-1, 0, 1}},`
	`15`	`+ {{-7, 3, 4}},`
	`16`	`+ }`
	`17`	`+`
	`18`	`+ for index, nums := range testData {`
	`19`	`+ if res := threeSum(nums); !reflect.DeepEqual(res, expected[index]) {`
	`20`	`+ t.Errorf("expected %v, got %v", expected[index], res)`
	`21`	`+ }`
	`22`	`+ }`
	`23`	`+}`

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`@@ -11,6 +11,7 @@`
`11`	`11`	\|0011\|[11. Container With Most Water](0011_container_with_most_water/container_with_most_water.go)\|Medium\|`array;` `double index`\|
`12`	`12`	\|0013\|[13. Roman to Integer](0013_roman_to_integer/roman_to_integer.go)\|Easy\|`math`\|
`13`	`13`	`\|0014\|[14. Longest Common Prefix](0014_longest_common_prefix/lcp.go)\|Easy\|\|`
	`14`	`+\|0015\|[15. 3Sum](0015_3Sum/3sum.go)\|Medium\|\|`
`14`	`15`	\|0017\|[Letter Combinations of a Phone Number](0017_letter_combination_of_a_phone_number/letter_combination_of_phone_number.go)\|Medium\|`tree`\|
`15`	`16`	\|0019\|[19. Remove Nth Node From End of List](0019_remove_nth_node_from_end_of_list/remove_nth_node_from_end_of_list.go)\|Medium\|`linked list`\|
`16`	`17`	\|0020\|[Valid Parentheses](0020_valid_parentheses/valid_parentheses.go)\|Easy\|`string;` `stack`\|

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