[leetcode] problem 509 – fibonacci number

The Fibonacci numbers, commonly denoted F(n) form a sequence, called the Fibonacci sequence, such that each number is the sum of the two preceding ones, starting from 0 and 1. That is,

F(0) = 0, F(1) = 1
F(N) = F(N - 1) + F(N - 2), for N > 1.

Given N, calculate F(N).

Example

No.1

No.2

No.3

Note

Code

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public int (int N) {
    if (N < 2)
        return N;

    int a = 0;
    int b = 1;

    for (int i = 2; i <= N; i++) {
        int sum = a + b;
        a = b;
        b = sum;
    }

    return b;
}