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51 lines
962 B
Markdown
Executable File
51 lines
962 B
Markdown
Executable File
# [1137. N-th Tribonacci Number](https://leetcode.com/problems/n-th-tribonacci-number/)
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## 题目
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The Tribonacci sequence Tn is defined as follows:
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T0 = 0, T1 = 1, T2 = 1, and Tn+3 = Tn + Tn+1 + Tn+2 for n >= 0.
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Given `n`, return the value of Tn.
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**Example 1:**
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Input: n = 4
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Output: 4
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Explanation:
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T_3 = 0 + 1 + 1 = 2
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T_4 = 1 + 1 + 2 = 4
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**Example 2:**
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Input: n = 25
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Output: 1389537
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**Constraints:**
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- `0 <= n <= 37`
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- The answer is guaranteed to fit within a 32-bit integer, ie. `answer <= 2^31 - 1`.
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## 题目大意
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泰波那契序列 Tn 定义如下：
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T0 = 0, T1 = 1, T2 = 1, 且在 n >= 0 的条件下 Tn+3 = Tn + Tn+1 + Tn+2
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给你整数 n，请返回第 n 个泰波那契数 Tn 的值。
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提示：
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- 0 <= n <= 37
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- 答案保证是一个 32 位整数，即 answer <= 2^31 - 1。
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## 解题思路
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- 求泰波那契数列中的第 n 个数。
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- 简单题，按照题意定义计算即可。
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