22w6: add 66 js solution

Author: swiftwind0405

README.md

@@ -377,7 +377,7 @@
 |69|[Sqrt(x)](https://leetcode.com/problems/sqrtx/)| |Medium|
 |68|[Text Justification](https://leetcode.com/problems/text-justification/)| |Hard|
 |67|[Add Binary](https://leetcode.com/problems/add-binary/)| [java](./algorithms/addBinary/Solution.java), [js](./algorithms/addBinary/Solution.js) |Easy|
-|66|[Plus One](https://leetcode.com/problems/plus-one/)| |Easy|
+|66|[Plus One](https://leetcode.com/problems/plus-one/)| [js](./algorithms/plusOne/solution.js) |Easy|
 |65|[Valid Number](https://leetcode.com/problems/valid-number/)| [js](./algorithms/validNumber/validNumber.js)  |Easy|
 |64|[Minimum Path Sum](https://leetcode.com/problems/minimum-path-sum/)| |Medium|
 |63|[Unique Paths II](https://leetcode.com/problems/unique-paths-ii/)| |Medium|

algorithms/plusOne/solution.js

@@ -0,0 +1,15 @@
+var plusOne = function(digits) {
+    let carry = true;  // 进位标志，初始化的时候末位是需要加1的
+    for (let index = digits.length - 1; index >= 0; index--) {
+        digits[index] = digits[index] + (carry ? 1 : 0); 
+        if (digits[index] > 9) {
+            // 溢出
+            digits[index] = 0;
+            carry = true;
+        } else {
+            carry = false;
+        }
+    }
+
+    return carry ? [1, ...digits] : digits;    // 最后如果依旧有进位标志，还需要处理一下
+};