adding Problem 16

试着往15上套，但是好像不大一样

Author: aQua

Algorithms/0016.3sum-closest/3sum-closest.go

@@ -1,2 +1,65 @@
 package Problem0016
 
+import (
+	"math"
+	"sort"
+)
+
+func threeSumClosest(nums []int, target int) int {
+
+	// 排序后，可以按规律查找
+	sort.Ints(nums)
+	res, delta := 0, math.MaxInt64
+
+	for i := range nums {
+		// 避免重复计算
+		if i > 0 && nums[i] == nums[i-1] {
+			continue
+		}
+
+		l, r := i+1, len(nums)-1
+
+		for l < r {
+			s := nums[i] + nums[l] + nums[r]
+			temp := abs(target - s)
+			switch {
+			case temp < delta:
+
+				l++
+			case s > 0:
+				// 较大的 r 需要变小
+				r--
+			default:
+				res = append(res, []int{nums[i], nums[l], nums[r]})
+				// 为避免重复添加，l 和 r 都需要移动到不同的元素上。
+				l, r = next(nums, l, r)
+			}
+		}
+	}
+
+	return res
+}
+
+func next(nums []int, l, r int) (int, int) {
+	for l < r {
+		switch {
+		case nums[l] == nums[l+1]:
+			l++
+		case nums[r] == nums[r-1]:
+			r--
+		default:
+			l++
+			r--
+			return l, r
+		}
+	}
+
+	return l, r
+}
+
+func abs(a int) int {
+	if a > 0 {
+		return a
+	}
+	return -a
+}

Algorithms/0016.3sum-closest/3sum-closest_test.go

@@ -1,8 +1,8 @@
 package Problem0016
 
 import (
-	"testing"
 	"fmt"
+	"testing"
 
 	"github.com/stretchr/testify/assert"
 )
@@ -15,13 +15,14 @@ type question struct {
 // para 是参数
 // one 代表第一个参数
 type para struct {
-	one string
+	one []int
+	two int
 }
 
 // ans 是答案
 // one 代表第一个答案
 type ans struct {
-	one string
+	one int
 }
 
 func Test_Problem0016(t *testing.T) {
@@ -30,17 +31,17 @@ func Test_Problem0016(t *testing.T) {
 	qs := []question{
 
 		question{
-			para{""},
-			ans{""},
+			para{[]int{-1, 2, 1, -4}, 1},
+			ans{2},
 		},
-	
+
 		// 如需多个测试，可以复制上方元素。
 	}
 
 	for _, q := range qs {
 		a, p := q.ans, q.para
 		fmt.Printf("~~%v~~\n", p)
 
-		ast.Equal(a.one, (p.one), "输入:%v", p)
+		ast.Equal(a.one, threeSumClosest(p.one, p.two), "输入:%v", p)
 	}
 }

Algorithms/0016.3sum-closest/README.md

@@ -1,8 +1,12 @@
 # [16. 3Sum Closest](https://leetcode.com/problems/3sum-closest/)
 
 ## 题目
+Given an array S of n integers, find three integers in S such that the sum is closest to a given number, target. Return the sum of the three integers. You may assume that each input would have exactly one solution.
+```
+For example, given array S = {-1 2 1 -4}, and target = 1.
 
-
+The sum that is closest to the target is 2. (-1 + 2 + 1 = 2).
+```
 ## 解题思路