Fibonacci Sequence

// Dynamic programming approach (memoization)

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

// Recursive approach

class Solution {
public:
    int fib(int n) {
        if(n < 2) return n;
        return fib(n-1) + fib(n-2);
    }
};