Merge pull request #572 from hitorig/master

Update 0046.全排列.md，更新了golang代码（原来的缺少permute函数）使用了切片思路 以及 第47题golang代码也有问题，同修改

problems/0046.全排列.md

@@ -227,24 +227,27 @@ class Solution:
 
 Go：
 ```Go
-var result [][]int
-func backtrack(nums,pathNums []int,used []bool){
-    if len(nums)==len(pathNums){
-        tmp:=make([]int,len(nums))
-        copy(tmp,pathNums)
-        result=append(result,tmp)
-        //result=append(result,pathNums)
-        return 
-    }
-    for i:=0;i<len(nums);i++{
-        if !used[i]{
-            used[i]=true
-            pathNums=append(pathNums,nums[i])
-            backtrack(nums,pathNums,used)
-            pathNums=pathNums[:len(pathNums)-1]
-            used[i]=false
-        }
-    }
+var res [][]int
+func permute(nums []int) [][]int {
+	res = [][]int{}
+	backTrack(nums,len(nums),[]int{})
+	return res
+}
+func backTrack(nums []int,numsLen int,path []int)  {
+	if len(nums)==0{
+		p:=make([]int,len(path))
+		copy(p,path)
+		res = append(res,p)
+	}
+	for i:=0;i<numsLen;i++{
+		cur:=nums[i]
+		path = append(path,cur)
+		nums = append(nums[:i],nums[i+1:]...)//直接使用切片
+		backTrack(nums,len(nums),path)
+		nums = append(nums[:i],append([]int{cur},nums[i:]...)...)//回溯的时候切片也要复原，元素位置不能变
+		path = path[:len(path)-1]
+
+	}
 }
 
 ```

problems/0047.全排列II.md

@@ -228,35 +228,31 @@ Go：
 ```go
 var res [][]int
 func permute(nums []int) [][]int {
-    res = [][]int{}
-    sort.Ints(nums)
-    dfs(nums, make([]int, 0), make([]bool, len(nums)))
-    return res
+	res = [][]int{}
+	backTrack(nums,len(nums),[]int{})
+	return res
 }
+func backTrack(nums []int,numsLen int,path []int)  {
+	if len(nums)==0{
+		p:=make([]int,len(path))
+		copy(p,path)
+		res = append(res,p)
+	}
+	used := [21]int{}//跟前一题唯一的区别，同一层不使用重复的数。关于used的思想carl在递增子序列那一题中提到过
+	for i:=0;i<numsLen;i++{
+		if used[nums[i]+10]==1{
+			continue
+		}
+		cur:=nums[i]
+		path = append(path,cur)
+		used[nums[i]+10]=1
+		nums = append(nums[:i],nums[i+1:]...)
+		backTrack(nums,len(nums),path)
+		nums = append(nums[:i],append([]int{cur},nums[i:]...)...)
+		path = path[:len(path)-1]
 
-func dfs(nums, path []int, used []bool) {
-    if len(path) == len(nums) {
-        res = append(res, append([]int{}, path...))
-        return
-    }
+	}
 
-    m := make(map[int]bool)
-    for i := 0; i < len(nums); i++ {
-        // used 从剩余 nums 中选
-        if used[i] {
-            continue
-        }
-        // m 集合间去重
-        if _, ok := m[nums[i]]; ok {
-            continue
-        }
-        m[nums[i]] = true
-        path = append(path, nums[i])
-        used[i] = true
-        dfs(nums, path, used)
-        used[i] = false
-        path = path[:len(path)-1]
-    }
 }
 ```