657. 机器人能否返回原点

Author: w2xi

Diff for: README.md

@@ -109,6 +109,7 @@
 |628|[三个数的最大乘积](https://leetcode.cn/problems/maximum-product-of-three-numbers/)|[JavaScript](./algorithms/maximum-product-of-three-numbers.js)|Easy|
 |637|[二叉树的层平均值](https://leetcode.cn/problems/average-of-levels-in-binary-tree/)|[JavaScript](./algorithms/average-of-levels-in-binary-tree.js)|Easy|
 |645|[错误的集合](https://leetcode.cn/problems/set-mismatch/)|[JavaScript](./algorithms/set-mismatch.js)|Easy|
+|657|[机器人能否返回原点](https://leetcode.cn/problems/robot-return-to-origin/)|[JavaScript](./algorithms/robot-return-to-origin.js)|Easy|
 |687|[最长同值路径](https://leetcode.cn/problems/longest-univalue-path/)|[JavaScript](./algorithms/longest-univalue-path.js)|Medium|
 |700|[二叉搜索树中的搜索](https://leetcode.cn/problems/search-in-a-binary-search-tree/)|[JavaScript](./algorithms/search-in-a-binary-search-tree.js)|Easy|
 |704|[二分查找](https://leetcode.cn/problems/binary-search/)|[JavaScript](./algorithms/binary-search.js)|Easy|

Diff for: algorithms/robot-return-to-origin.js

@@ -0,0 +1,36 @@
+/**
+ * @param {string} moves
+ * @return {boolean}
+ */
+var judgeCircle = function (moves) {
+  // 思路:
+  // 要回到原点，'L' 出现的次数 等于 'R' 且 'U' 出现的次数等于 'D'
+  // 空间复杂度: O(n)
+
+  let o = {};
+
+  for (let char of moves) {
+    o[char] = (o[char] || 0) + 1;
+  }
+  if (o["L"] === o["R"] && o["U"] === o["D"]) {
+    return true;
+  } else {
+    return false;
+  }
+
+  // 思路:
+  // 将物体的前后左右移动看成是在 xy 坐标轴上的移动
+  // 空间复杂度: O(1)
+
+  // let x = 0,
+  //   y = 0;
+
+  // for (let char of moves) {
+  //   if (char === "R") x++;
+  //   if (char === "L") x--;
+  //   if (char === "U") y++;
+  //   if (char === "D") y--;
+  // }
+
+  // return x === 0 && y === 0;
+};