[17] 电话号码的字母组合

src/leecode/javascript/17.电话号码的字母组合.js

@@ -0,0 +1,45 @@
+/*
+ * @lc app=leetcode.cn id=17 lang=javascript
+ *
+ * [17] 电话号码的字母组合
+ */
+
+// @lc code=start
+/**
+ * @param {string} digits
+ * @return {string[]}
+ */
+const keymap = [
+  [],
+  [],
+  ['a', 'b', 'c'],
+  ['d', 'e', 'f'],
+  ['g', 'h', 'i'],
+  ['j', 'k', 'l'],
+  ['m', 'n', 'o'],
+  ['p', 'q', 'r', 's'],
+  ['t', 'u', 'v'],
+  ['w', 'x', 'y', 'z'],
+];
+var letterCombinations = function (digits) {
+  const result = [];
+  if (digits.length === 0) {
+    return result;
+  }
+  def('', 0, digits, result);
+  return result;
+};
+
+const def = function (ret, index, digits, arr) {
+  if (index >= digits.length) {
+    arr.push(ret);
+    return;
+  }
+  for (const letter of keymap[parseInt(digits[index])]) {
+    ret += letter;
+    def(ret, index + 1, digits, arr);
+    ret = ret.slice(0, -1);
+  }
+};
+
+// @lc code=end