add: Z 字形变换

.vscode/settings.json

@@ -23,6 +23,9 @@
     "mincost",
     "nums",
     "Paddr",
+    "PAHNAPLSIIGYIR",
+    "PAYPALISHIRING",
+    "PINALSIGYAHRPI",
     "powx",
     "preorder",
     "Prinme",

README.md

@@ -391,6 +391,10 @@ TypeScript / JavaScript 基础算法、数据结构练习，包含 LeetCode 或
 
   - LeetCode 710. 黑名单中的随机数 <https://leetcode.cn/problems/random-pick-with-blacklist/>
 
+- [Z 字形变换](src/array/zigzag-conversion.ts)
+
+  - LeetCode 6. Z 字形变换 <https://leetcode.cn/problems/zigzag-conversion/>
+
 ## 栈
 
 - [最大矩阵](src/stack/maximal-rectangle.js)

src/array/zigzag-conversion.ts

@@ -0,0 +1,16 @@
+export function convert (s: string, numRows: number): string {
+  if (numRows === 1) return s
+  const res = new Array(numRows).fill('')
+
+  for (let i = 0, len = s.length, isDown = true, row = 0; i < len; i++) {
+    res[isDown ? row++ : row--] += s[i]
+
+    if (row === numRows - 1) {
+      isDown = false
+    } else if (row === 0) {
+      isDown = true
+    }
+  }
+
+  return res.join('')
+}

test/array/zigzag-conversion.test.ts

@@ -0,0 +1,8 @@
+import { convert } from '../../src/array/zigzag-conversion'
+
+test('Z 字形变换', () => {
+  expect(convert('PAYPALISHIRING', 3)).toBe('PAHNAPLSIIGYIR')
+  expect(convert('PAYPALISHIRING', 4)).toBe('PINALSIGYAHRPI')
+  expect(convert('A', 1)).toBe('A')
+  expect(convert('AB', 1)).toBe('AB')
+})