Merge pull request #325 from flames519/master

回溯，组合分割 JavaScript版本

Author: youngyangyang04

problems/0017.电话号码的字母组合.md

@@ -137,7 +137,7 @@ for (int i = 0; i < letters.size(); i++) {
 关键地方都讲完了，按照[关于回溯算法，你该了解这些！](https://mp.weixin.qq.com/s/gjSgJbNbd1eAA5WkA-HeWw)中的回溯法模板，不难写出如下C++代码：
 
 
-```
+```c++
 // 版本一
 class Solution {
 private:
@@ -183,7 +183,7 @@ public:
 
 一些写法，是把回溯的过程放在递归函数里了，例如如下代码，我可以写成这样：（注意注释中不一样的地方）
 
-```
+```c++
 // 版本二
 class Solution {
 private:
@@ -319,7 +319,7 @@ class Solution:
 
 python3：
 
-```python3
+```py
 class Solution:
     def letterCombinations(self, digits: str) -> List[str]:
         self.s = ""
@@ -342,6 +342,33 @@ class Solution:
 
 Go：
 
+javaScript：
+
+```js
+var letterCombinations = function(digits) {
+    const k = digits.length;
+    const map = ["","","abc","def","ghi","jkl","mno","pqrs","tuv","wxyz"];
+    if(!k) return [];
+    if(k === 1) return map[digits].split("");
+
+    const res = [], path = [];
+    backtracking(digits, k, 0);
+    return res;
+
+    function backtracking(n, k, a) {
+        if(path.length === k) {
+            res.push(path.join(""));
+            return;
+        }
+        for(const v of map[n[a]]) {
+            path.push(v);
+            backtracking(n, k, a + 1);
+            path.pop();
+        }
+
+    }
+};
+```
 
 
 

problems/0039.组合总和.md

@@ -286,30 +286,30 @@ class Solution:
 ```
 Go：
 
-JavaScript
+JavaScript：
+
 ```js
-var strStr = function (haystack, needle) {
-  if (needle === '') {
-    return 0;
-  }
-
-  let hayslen = haystack.length;
-  let needlen = needle.length;
-
-  if (haystack === '' || hayslen < needlen) {
-    return -1;
-  }
-
-  for (let i = 0; i <= hayslen - needlen; i++) {
-    if (haystack[i] === needle[0]) {
-      if (haystack.substr(i, needlen) === needle) {
-        return i;
-      }
-    }
-    if (i === hayslen - needlen) {
-      return -1;
+var combinationSum = function(candidates, target) {
+    const res = [], path = [];
+    candidates.sort(); // 排序
+    backtracking(0, 0);
+    return res;
+    function backtracking(j, sum) {
+        if (sum > target) return;
+        if (sum === target) {
+            res.push(Array.from(path));
+            return;
+        }
+        for(let i = j; i < candidates.length; i++ ) {
+            const n = candidates[i];
+            if(n > target - sum) continue;
+            path.push(n);
+            sum += n;
+            backtracking(i, sum);
+            path.pop();
+            sum -= n;
+        }
     }
-  }
 };
 ```
 

problems/0040.组合总和II.md

@@ -293,7 +293,7 @@ class Solution {
 }
 ```
 Python：
-```python3
+```py
 class Solution:
     def combinationSum2(self, candidates: List[int], target: int) -> List[List[int]]:
         res = []
@@ -314,7 +314,39 @@ class Solution:
 ```
 Go：
 
-
+javaScript： 
+
+```js
+/**
+ * @param {number[]} candidates
+ * @param {number} target
+ * @return {number[][]}
+ */
+var combinationSum2 = function(candidates, target) {
+    const res = []; path = [], len = candidates.length;
+    candidates.sort();
+    backtracking(0, 0);
+    return res;
+    function backtracking(sum, i) {
+        if (sum > target) return;
+        if (sum === target) {
+            res.push(Array.from(path));
+            return;
+        }
+        let f = -1;
+        for(let j = i; j < len; j++) {
+            const n = candidates[j];
+            if(n > target - sum || n === f) continue;
+            path.push(n);
+            sum += n;
+            f = n;
+            backtracking(sum, j + 1);
+            path.pop();
+            sum -= n;
+        }
+    }
+};
+```
 
 
 -----------------------

problems/0077.组合优化.md

@@ -147,7 +147,7 @@ public:
 
 
 Java：
-```
+```java
 class Solution {
     List<List<Integer>> result = new ArrayList<>();
     LinkedList<Integer> path = new LinkedList<>();
@@ -220,6 +220,28 @@ func backtrack(n,k,start int,track []int){
 }
 ```
 
+javaScript:
+
+```js
+var combine = function(n, k) {
+    const res = [], path = [];
+    backtracking(n, k, 1);
+    return res;
+    function backtracking (n, k, i){
+        const len = path.length;
+        if(len === k) {
+            res.push(Array.from(path));
+            return;
+        }
+        for(let a = i; a <= n + len - k + 1; a++) {
+            path.push(a);
+            backtracking(n, k, a + 1);
+            path.pop();
+        }
+    }
+};
+```
+
 
 
 

problems/0093.复原IP地址.md

@@ -338,6 +338,35 @@ class Solution(object):
         return ans```
 ```
 
+JavaScript： 
+
+```js
+/**
+ * @param {string} s
+ * @return {string[]}
+ */
+var restoreIpAddresses = function(s) {
+    const res = [], path = [];
+    backtracking(0, 0)
+    return res;
+    function backtracking(i) {
+        const len = path.length;
+        if(len > 4) return;
+        if(len === 4 && i === s.length) {
+            res.push(path.join("."));
+            return;
+        }
+        for(let j = i; j < s.length; j++) {
+            const str = s.substr(i, j - i + 1);
+            if(str.length > 3 || +str > 255) break;
+            if(str.length > 1 && str[0] === "0") break;
+            path.push(str);
+            backtracking(j + 1);
+            path.pop()
+        }
+    }
+};
+```
 
 -----------------------
 * 作者微信：[程序员Carl](https://mp.weixin.qq.com/s/b66DFkOp8OOxdZC_xLZxfw)

problems/0131.分割回文串.md

@@ -292,7 +292,7 @@ class Solution {
 ```
 
 Python：
-```python3
+```py
 class Solution:
     def partition(self, s: str) -> List[List[str]]:
         res = []  
@@ -313,7 +313,38 @@ class Solution:
 
 Go：
 
+javaScript：
 
+```js
+/**
+ * @param {string} s
+ * @return {string[][]}
+ */
+const isPalindrome = (s, l, r) => {
+    for (let i = l, j = r; i < j; i++, j--) {
+        if(s[i] !== s[j]) return false;
+    }
+    return true;
+}
+
+var partition = function(s) {
+    const res = [], path = [], len = s.length;
+    backtracking(0);
+    return res;
+    function backtracking(i) {
+        if(i >= len) {
+            res.push(Array.from(path));
+            return;
+        }
+        for(let j = i; j < len; j++) {
+            if(!isPalindrome(s, i, j)) continue;
+            path.push(s.substr(i, j - i + 1));
+            backtracking(j + 1);
+            path.pop();
+        }
+    }
+};
+```
 
 
 -----------------------

problems/0216.组合总和III.md

@@ -180,7 +180,7 @@ if (sum > targetSum) { // 剪枝操作
 
 最后C++代码如下：
 
-```
+```c++
 class Solution {
 private:
     vector<vector<int>> result; // 存放结果集
@@ -262,7 +262,7 @@ class Solution {
 ```
 
 Python：
-```python3
+```py
 class Solution:
     def combinationSum3(self, k: int, n: int) -> List[List[int]]:
         res = []  #存放结果集
@@ -284,6 +284,44 @@ class Solution:
 
 Go：
 
+javaScript:
+
+```js
+// 等差数列
+var maxV = k => k * (9 + 10 - k) / 2;
+var minV = k => k * (1 + k) / 2;
+var combinationSum3 = function(k, n) {
+    if (k > 9 || k < 1) return [];
+    // if (n > maxV(k) || n < minV(k)) return [];
+    // if (n === maxV(k)) return [Array.from({length: k}).map((v, i) => 9 - i)];
+    // if (n === minV(k)) return [Array.from({length: k}).map((v, i) => i + 1)];
+
+    const res = [], path = [];
+    backtracking(k, n, 1, 0);
+    return res;
+    function backtracking(k, n, i, sum){
+        const len = path.length;
+        if (len > k || sum > n) return;
+        if (maxV(k - len) < n - sum) return;
+        if (minV(k - len) > n - sum) return; 
+
+        if(len === k && sum == n) {
+            res.push(Array.from(path));
+            return;
+        }
+
+        const min = Math.min(n - sum, 9 + len - k + 1);
+
+        for(let a = i; a <= min; a++) {
+            path.push(a);
+            sum += a;
+            backtracking(k, n, a + 1, sum);
+            path.pop();
+            sum -= a;
+        }
+    }
+};
+```