leetcode 6. Zigzag Conversion

Algorithm/Other/at coder/Other/leetcode/6. Zigzag Conversion/README.md

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+
+```ts
+function convert(s: string, numRows: number): string {
+    if (numRows === 1 || s.length <= numRows) return s;
+
+    const rows: string[] = Array(Math.min(numRows, s.length)).fill("");
+    let currentRow = 0;
+    let goingDown = false;
+
+    for (const char of s) {
+        rows[currentRow] += char;
+
+        // 一番上または一番下に到達したら方向を反転
+        if (currentRow === 0 || currentRow === numRows - 1) {
+            goingDown = !goingDown;
+        }
+
+        currentRow += goingDown ? 1 : -1;
+    }
+
+    return rows.join("");
+}
+```
+
+---
+
+### 🔍 実行例:
+
+#### 入力1:
+
+```ts
+console.log(convert("PAYPALISHIRING", 3));
+```
+
+出力:
+
+```
+"PAHNAPLSIIGYIR"
+```
+
+#### 入力2:
+
+```ts
+console.log(convert("PAYPALISHIRING", 4));
+```
+
+出力:
+
+```
+"PINALSIGYAHRPI"
+```
+
+#### 入力3:
+
+```ts
+console.log(convert("A", 1));
+```
+
+出力:
+
+```
+"A"
+```
+
+---
+
+### 🧠 アルゴリズムの考え方（図付き）
+
+例: `s = "PAYPALISHIRING", numRows = 4`
+
+```
+P     I    N
+A   L S  I G
+Y A   H R
+P     I
+```
+
+* 各文字を1文字ずつ `rows[]` に追加
+* 上から下に移動し、最下段に達したら反転して上に戻るというパターン
+* 方向はフラグ `goingDown` で管理
+
+---

Algorithm/Other/at coder/Other/leetcode/6. Zigzag Conversion/ZigzagConversion.ts

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+function convert(s: string, numRows: number): string {
+    if (numRows === 1 || s.length <= numRows) return s;
+
+    const rows: string[] = Array(Math.min(numRows, s.length)).fill('');
+    let currentRow = 0;
+    let goingDown = false;
+
+    for (const char of s) {
+        rows[currentRow] += char;
+
+        // 一番上または一番下に到達したら方向を反転
+        if (currentRow === 0 || currentRow === numRows - 1) {
+            goingDown = !goingDown;
+        }
+
+        currentRow += goingDown ? 1 : -1;
+    }
+
+    return rows.join('');
+}