commit solution 15

Author: lxlxw

Diff for: index-tags.md

@@ -8,6 +8,7 @@
 | --- | --- | --- | --- | --- |
 |  [1](https://leetcode-cn.com/problems/two-sum)  |  [两数之和](/solution/1-99/0001.two-sum/)  |  `数组`,`哈希表`  |  <font color=green>简单</font>  | ✅ |
 |  [11](https://leetcode-cn.com/problems/container-with-most-water)  |  [盛最多水的容器](/solution/1-99/0011.container-with-most-water/)  |  `数组`,`双指针`  |  <font color=blue>中等</font>  |✅ |
+|  [15](https://leetcode-cn.com/problems/3sum)  |  [三数之和](/solution/1-99/0015.3sum/)  |  `数组`,`双指针`  |  <font color=blue>中等</font>  |✅ |
 |  [26](https://leetcode-cn.com/problems/remove-duplicates-from-sorted-array)  |  [删除排序数组中的重复项](/solution/1-99/0026.remove-duplicates-from-sorted-array/)  |  `数组`,`双指针`  |  <font color=green>简单</font>  |✅ |
 |  [27](https://leetcode-cn.com/problems/remove-element)  |  [移除元素](/solution/1-99/0027.remove-element/)  |  `数组`,`双指针`  |  <font color=green>简单</font>  |✅ |
 |  [35](https://leetcode-cn.com/problems/search-insert-position)  |  [搜索插入位置](/solution/1-99/0035.search-insert-position/)  |  `数组`,`二分查找`  |  <font color=green>简单</font>  |✅ |
@@ -67,6 +68,7 @@
 |  题号  |  题解  |  标签  | 难度  | 是否解题 |
 | --- | --- | --- | --- | --- |
 |  [11](https://leetcode-cn.com/problems/container-with-most-water)  |  [盛最多水的容器](/solution/1-99/0011.container-with-most-water/)  |  `数组`,`双指针`  |  <font color=blue>中等</font>  |✅ |
+|  [15](https://leetcode-cn.com/problems/3sum)  |  [三数之和](/solution/1-99/0015.3sum/)  |  `数组`,`双指针`  |  <font color=blue>中等</font>  |✅ |
 |  [26](https://leetcode-cn.com/problems/remove-duplicates-from-sorted-array)  |  [删除排序数组中的重复项](/solution/1-99/0026.remove-duplicates-from-sorted-array/)  |  `数组`,`双指针`  |  <font color=green>简单</font>  |✅ |
 |  [27](https://leetcode-cn.com/problems/remove-element)  |  [移除元素](/solution/1-99/0027.remove-element/)  |  `数组`,`双指针`  |  <font color=green>简单</font>  |✅ |
 |  [28](https://leetcode-cn.com/problems/implement-strstr)  |  [实现 strstr()](/solution/1-99/0028.implement-strstr%28%29/)  |  `双指针`,`字符串`  |  <font color=green>简单</font>  |✅ |

Diff for: index-type.md

@@ -412,7 +412,7 @@
 |  [8](https://leetcode-cn.com/problems/string-to-integer-atoi)  |  [字符串转换整数 (atoi)](/solution/1-99/0008.string-to-integer-%28atoi%29/)  |  `数学`,`字符串`  |  <font color=blue>中等</font>  |
 |  [11](https://leetcode-cn.com/problems/container-with-most-water)  |  [盛最多水的容器](/solution/1-99/0011.container-with-most-water/)  |  `数组`,`双指针`  |  <font color=blue>中等</font>  |✅ |
 |  [12](https://leetcode-cn.com/problems/integer-to-roman)  |  [整数转罗马数字](/solution/1-99/0012.integer-to-roman/)  |  `数学`,`字符串`  |  <font color=blue>中等</font>  |
-|  [15](https://leetcode-cn.com/problems/3sum)  |  [三数之和](/solution/1-99/0015.3sum/)  |  `数组`,`双指针`  |  <font color=blue>中等</font>  |
+|  [15](https://leetcode-cn.com/problems/3sum)  |  [三数之和](/solution/1-99/0015.3sum/)  |  `数组`,`双指针`  |  <font color=blue>中等</font>  |✅ |
 |  [16](https://leetcode-cn.com/problems/3sum-closest)  |  [最接近的三数之和](/solution/1-99/0016.3sum-closest/)  |  `数组`,`双指针`  |  <font color=blue>中等</font>  |
 |  [17](https://leetcode-cn.com/problems/letter-combinations-of-a-phone-number)  |  [电话号码的字母组合](/solution/1-99/0017.letter-combinations-of-a-phone-number/)  |  `字符串`,`回溯算法`  |  <font color=blue>中等</font>  |
 |  [18](https://leetcode-cn.com/problems/4sum)  |  [四数之和](/solution/1-99/0018.4sum/)  |  `数组`,`哈希表`,`双指针`  |  <font color=blue>中等</font>  |

Diff for: solution/1-99/0015.3sum/README.md

@@ -1,20 +1,61 @@
-# [15. xxx](https://leetcode-cn.com/problems/longest-common-prefix)
+# [15. 三数之和](https://leetcode-cn.com/problems/3sum/description/)
 
 ### 题目描述
 
+<p>给你一个包含 <em>n</em> 个整数的数组&nbsp;<code>nums</code>，判断&nbsp;<code>nums</code>&nbsp;中是否存在三个元素 <em>a，b，c ，</em>使得&nbsp;<em>a + b + c = </em>0 ？请你找出所有满足条件且不重复的三元组。</p>
 
+<p><strong>注意：</strong>答案中不可以包含重复的三元组。</p>
+
+<p>&nbsp;</p>
+
+<p><strong>示例：</strong></p>
+
+<pre>给定数组 nums = [-1, 0, 1, 2, -1, -4]，
+
+满足要求的三元组集合为：
+[
+  [-1, 0, 1],
+  [-1, -1, 2]
+]
+</pre>
 
 ### 解题思路
 
+![](http://lc-photo.xwlin.com/15.gif)
 
 ### 具体解法
 
-<!-- tabs:start -->
-
 #### **Golang**
 ```go
-
+func threeSum(nums []int) [][]int {
+	sort.Ints(nums)
+	flagMap := make(map[string]bool)
+	var res [][]int
+	i := 0
+	for i < len(nums) {
+		if i-1 >= 0 && nums[i] == nums[i-1] {
+			i++
+			continue
+		}
+		p, q := 1, len(nums)-1
+		for p+i < q {
+			if nums[i]+nums[p+i]+nums[q] == 0 {
+				flag := strconv.Itoa(nums[i]) + strconv.Itoa(nums[p+i]) + strconv.Itoa(nums[q])
+				if _, ok := flagMap[flag]; !ok {
+					res = append(res, []int{nums[i], nums[p+i], nums[q]})
+				}
+				flagMap[flag] = true
+				p++
+				q--
+			} else if nums[i]+nums[p+i]+nums[q] > 0 {
+				q--
+			} else if nums[i]+nums[p+i]+nums[q] < 9 {
+				p++
+			}
+		}
+		i++
+	}
+	return res
+}
 ```
 
-<!-- tabs:end -->
-

Diff for: solution/1-99/0015.3sum/solution.go

@@ -0,0 +1,46 @@
+package leetcode
+
+import (
+	"sort"
+	"strconv"
+)
+
+/*
+ * @lc app=leetcode.cn id=15 lang=golang
+ *
+ * [15] 三数之和
+ */
+
+// @lc code=start
+func threeSum(nums []int) [][]int {
+	sort.Ints(nums)
+	flagMap := make(map[string]bool)
+	var res [][]int
+	i := 0
+	for i < len(nums) {
+		if i-1 >= 0 && nums[i] == nums[i-1] {
+			i++
+			continue
+		}
+		p, q := 1, len(nums)-1
+		for p+i < q {
+			if nums[i]+nums[p+i]+nums[q] == 0 {
+				flag := strconv.Itoa(nums[i]) + strconv.Itoa(nums[p+i]) + strconv.Itoa(nums[q])
+				if _, ok := flagMap[flag]; !ok {
+					res = append(res, []int{nums[i], nums[p+i], nums[q]})
+				}
+				flagMap[flag] = true
+				p++
+				q--
+			} else if nums[i]+nums[p+i]+nums[q] > 0 {
+				q--
+			} else if nums[i]+nums[p+i]+nums[q] < 9 {
+				p++
+			}
+		}
+		i++
+	}
+	return res
+}
+
+// @lc code=end

Diff for: solution/1-99/0015.3sum/solution_test.go

@@ -0,0 +1,20 @@
+package leetcode
+
+import (
+	"testing"
+)
+
+func TestThreeSum(t *testing.T) {
+	var ret [][]int
+	var nums []int
+
+	nums = []int{-1, 0, 1, 2, -1, -4}
+	ret = [][]int{{-1, -1, 2}, {-1, 0, 1}}
+	for k, num := range threeSum(nums) {
+		for i, v := range num {
+			if v != ret[k][i] {
+				t.Fatalf("case fails %v\n", ret)
+			}
+		}
+	}
+}

Diff for: solution/1-99/_sidebar.md

@@ -20,7 +20,7 @@
     - [12. 整数转罗马数字](solution/1-99/0012.integer-to-roman/)
     - [13. 罗马数字转整数 ✅](solution/1-99/0013.roman-to-integer/)
     - [14. 最长公共前缀](solution/1-99/0014.longest-common-prefix/)
-    - [15. 三数之和](solution/1-99/0015.3sum/)
+    - [15. 三数之和 ✅](solution/1-99/0015.3sum/)
     - [16. 最接近的三数之和](solution/1-99/0016.3sum-closest/)
     - [17. 电话号码的字母组合](solution/1-99/0017.letter-combinations-of-a-phone-number/)
     - [18. 四数之和](solution/1-99/0018.4sum/)