509. Fibonacci Number

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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 1:

Input: n = 2
Output: 1
Explanation: F(2) = F(1) + F(0) = 1 + 0 = 1.
Example 2:

Input: n = 3
Output: 2
Explanation: F(3) = F(2) + F(1) = 1 + 1 = 2.
Example 3:

Input: n = 4
Output: 3
Explanation: F(4) = F(3) + F(2) = 2 + 1 = 3.
 

Constraints:

0 <= n <= 30
Accepted
1.2M
Submissions
1.8M
Acceptance Rate
69.6%

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class Solution {
public:
int fib(int N) {
        if(N < 2)
            return N;
        int memo[N+1];
        memo[0] = 0;
        memo[1] = 1;
        for(int i=2; i<=N; i++)
            memo[i] = memo[i-1] + memo[i-2];
        return memo[N];
    }};