add dfs

Author: itcuihao

problems/0017.letter-combinations-of-a-phone-number/README.md

@@ -1,7 +1,11 @@
 Given a string containing digits from 2-9 inclusive, return all possible letter combinations that the number could represent.
 
+
 A mapping of digit to letters (just like on the telephone buttons) is given below. Note that 1 does not map to any letters.
 
+<p align="center">
+<img src=http://on64lz47x.bkt.clouddn.com/leetcode17.png>
+</p>
 
 Example:
 
@@ -10,4 +14,3 @@ Input: "23"
 Output: ["ad", "ae", "af", "bd", "be", "bf", "cd", "ce", "cf"].
 ```
 
->构建map循环

problems/0017.letter-combinations-of-a-phone-number/run.go

@@ -1,15 +1,17 @@
 package closest
 
+import "fmt"
 
-var jp = []string{"", "", "abc", "def", "ghi", "jkl", "mno", "pqrs", "tuv", "wxyz"}
+// bfs
 func letterCombinations(digits string) []string {
+	var jp = []string{"", "", "abc", "def", "ghi", "jkl", "mno", "pqrs", "tuv", "wxyz"}
 	ld := len(digits)
 	// 初始化
 	r := []string{}
 	if ld == 0 {
 		return r
 	}
-r=[]string{""}
+	r = []string{""}
 	for i := 0; i < ld; i++ {
 		var tmp []string
 		// 获取jp对应的下标
@@ -24,3 +26,32 @@ r=[]string{""}
 	}
 	return r
 }
+
+// dfs
+func letterCombinationsDFS(digits string) []string {
+	var jp = []string{"", "", "abc", "def", "ghi", "jkl", "mno", "pqrs", "tuv", "wxyz"}
+	cur := make([]rune, len(digits))
+	ans = dfs(digits, jp, 0, cur)
+	return ans
+}
+
+var (
+	ans []string
+)
+
+func dfs(digits string, jp []string, l int, cur []rune) []string {
+
+	if l == len(digits) {
+		if l > 0 {
+			ans = append(ans, string(cur))
+		}
+		return ans
+	}
+	s := jp[digits[l]-'0']
+	for _, v := range s {
+		cur[l] = v
+		fmt.Println("cur:", string(cur))
+		ans = dfs(digits, jp, l+1, cur)
+	}
+	return ans
+}

problems/0017.letter-combinations-of-a-phone-number/run_test.go

@@ -9,6 +9,7 @@ func TestRun(t *testing.T) {
 
 	target := "23"
 
-	s := letterCombinations(target)
+	// s := letterCombinations(target)
+	s := letterCombinationsDFS(target)
 	fmt.Println(s)
 }