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1137. 第 N 个泰波那契数

泰波那契序列 Tn 定义如下：

T0 = 0, T1 = 1, T2 = 1, 且在 n >= 0 的条件下 Tn+3 = Tn + Tn+1 + Tn+2

给你整数 n，请返回第 n 个泰波那契数 Tn 的值。

链接

function tribonacci(n: number): number {
  const dpTable: Record<number, number> = {};
  dpTable[0] = 0;
  dpTable[1] = 1;
  dpTable[2] = 1;
  if (n < 3) return dpTable[n];
  const handleCount = (target: number) => {
    if (dpTable[target] !== undefined) return dpTable[target]
    const result = handleCount(target - 2) + handleCount(target - 1) + handleCount(target - 3);
    dpTable[target] = result;
    return result;
  };
  return handleCount(n);
};