[pull] master from youngyangyang04:master

problems/0093.复原IP地址.md

@@ -444,7 +444,7 @@ var restoreIpAddresses = function(s) {
             return;
         }
         for(let j = i; j < s.length; j++) {
-            const str = s.substr(i, j - i + 1);
+            const str = s.slice(i, j + 1);
             if(str.length > 3 || +str > 255) break;
             if(str.length > 1 && str[0] === "0") break;
             path.push(str);

problems/0131.分割回文串.md

@@ -442,7 +442,7 @@ var partition = function(s) {
         }
         for(let j = i; j < len; j++) {
             if(!isPalindrome(s, i, j)) continue;
-            path.push(s.substr(i, j - i + 1));
+            path.push(s.slice(i, j + 1));
             backtracking(j + 1);
             path.pop();
         }

problems/0216.组合总和III.md

@@ -360,39 +360,30 @@ func backTree(n,k,startIndex int,track *[]int,result *[][]int){
 ## javaScript
 
 ```js
-// 等差数列
-var maxV = k => k * (9 + 10 - k) / 2;
-var minV = k => k * (1 + k) / 2;
+/**
+ * @param {number} k
+ * @param {number} n
+ * @return {number[][]}
+ */
 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));
+    const backtrack = (start) => {
+        const l = path.length;
+        if (l === k) {
+            const sum = path.reduce((a, b) => a + b);
+            if (sum === n) {
+                res.push([...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);
+        for (let i = start; i <= 9 - (k - l) + 1; i++) {
+            path.push(i);
+            backtrack(i + 1);
             path.pop();
-            sum -= a;
         }
     }
+    let res = [], path = [];
+    backtrack(1);
+    return res;
 };
 ```