add: 只出现一次的数字等

test/math/permutations.test.js

@@ -0,0 +1,12 @@
+import { permute } from '../../src/math/permutations'
+
+test('全排列', () => {
+  expect(permute([1, 2, 3])).toEqual([
+    [1, 2, 3],
+    [1, 3, 2],
+    [2, 1, 3],
+    [2, 3, 1],
+    [3, 1, 2],
+    [3, 2, 1]
+  ])
+})