feat: 电话号码的字母组合

DFS问题/电话号码的字母组合-17.js

@@ -0,0 +1,48 @@
+/**
+ * @param {string} digits
+ * @return {string[]}
+ */
+let letterMap = [
+  " ", //0
+  "", //1
+  "abc", //2
+  "def", //3
+  "ghi", //4
+  "jkl", //5
+  "mno", //6
+  "pqrs", //7
+  "tuv", //8
+  "wxyz", //9
+]
+
+let letterCombinations = function (digits) {
+  let res = []
+
+  if (digits === "") {
+    return res
+  }
+
+  /**
+   *
+   * @param {number} index 当前处理到的下标位置
+   * @param {string} str 当前已经凑成的字符串
+   */
+  let findCombinations = (index, str) => {
+    if (digits.length === index) {
+      res.push(str)
+      return
+    }
+
+    let char = digits[index] // 数字
+    let letters = letterMap[Number(char)] // 数字对应的字母
+
+    for (let i = 0; i < letters.length; i++) {
+      let letter = letters[i]
+      findCombinations(index + 1, `${str}${letter}`)
+    }
+  }
+
+  findCombinations(0, "")
+
+  return res
+}