1
var pyramidTransition = function (bottom, allowed) {
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  const set = new Set(allowed);
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  const memo = new Map();
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  const chars = ["A", "B", "C", "D", "E", "F"];
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  return topDown(bottom, bottom.length - 1);
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  function topDown(prev, row) {
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    const key = `${prev}#${row}`;
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    if (row === 0) return true;
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    if (memo.has(key)) return memo.get(key);
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    let pats = new Set();
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    pats.add("");
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    for (let i = 0; i < row; i++) {
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      const tmp = new Set();
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      const leftBot = prev.charAt(i);
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      const rightBot = prev.charAt(i + 1);
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      for (const char of chars) {
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        const triadStr = leftBot + rightBot + char;
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        if (set.has(triadStr)) {
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          for (const pat of pats) {
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            tmp.add(pat + char);
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          }
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        }
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      }
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      pats = tmp;
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    }
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    for (const pat of pats) {
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      if (topDown(pat, row - 1)) return true;
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    }
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    memo.set(key, false);
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    return false;
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  }
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};