定制 2048 合成游戏的晋升词条

只是写法示意，不是完整程序。

// ANS 2048 单行向左滑动压缩与同级合并纯函数 (ans-2048-merge.ts)
export function slideAndMergeAnsRow(row: number[]) {
  const nonZero = row.filter((n) => n > 0);
  const out: number[] = [];
  let gained = 0;
  for (let i = 0; i < nonZero.length; i++) {
    if (nonZero[i] === nonZero[i + 1]) { const merged = nonZero[i] * 2; out.push(merged); gained += merged; i++; }
    else out.push(nonZero[i]);
  }
  while (out.length < 4) out.push(0);
  return { row: out, gained };
}