首页 > ACM题库 > HDU-杭电 > HDU 2793-HOJ-Sum of Tribonacci Numbers-待解决[解题报告]C++
2014
02-14

HDU 2793-HOJ-Sum of Tribonacci Numbers-待解决[解题报告]C++

Sum of Tribonacci Numbers

问题描述 :

Everybody knows Fibonacci numbers, now we are talking about the Tribonacci numbers:
T[0] = T[1] = T[2] = 1;
T[n] = T[n - 1] + T[n - 2] + T[n - 3] (n >= 3)Given a and b, you are asked to calculate the sum from the ath Fibonacci number to the bth Fibonacci number, mod 1,000,000,007, that is (T[a] + T[a + 1] + … + T[b]) % 1,000,000,007.

输入:

There are multiple cases (no more than 100).Each case contain two non-negative integers a b(a <= b and a, b < 1,000,000,000)

输出:

There are multiple cases (no more than 100).Each case contain two non-negative integers a b(a <= b and a, b < 1,000,000,000)

样例输入:

0 2
0 5

样例输出:

3
20

 


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