add: 只出现一次的数字等

src/math/permutations.js

@@ -0,0 +1,15 @@
+/**
+ * @param {number[]} nums
+ * @return {number[][]}
+ */
+export const permute = function (nums) {
+  const res = []
+  const backtrack = (path = []) => {
+    if (path.length === nums.length) res.push(path)
+    for (const n of nums) {
+      !path.includes(n) && backtrack(path.concat(n))
+    }
+  }
+  backtrack()
+  return res
+}