动态规划

#include
#include
#include

using namespace std;

//斐波那契数列 重复计算
/*
long Fibonacci(unsigned int n)
{
	if (n == 0)
		return 0;
	
	if (n == 1)
		return 1;
	
	else
		return Fibonacci(n - 1) + Fibonacci(n - 2);
}
*/

// 怎么减小计算量 加一个记忆
// 记忆化搜索
/*
vector memo;
long Fibonacci(unsigned int n)
{
	if (n == 0)
		return 0;
	
	if (n == 1)
		return 1;
	
	if(memo[n]==-1)
		memo[n] = Fibonacci(n - 1) + Fibonacci(n - 2);
	
	return memo[n];
}
*/

// 动态规划
long Fibonacci(unsigned int n)
{
	vector memo(n+1,-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];
}



int main()
{
	unsigned int num = 0;
	cin >> num;
	
	time_t startTime = clock();
	long res = Fibonacci(num);
	time_t endTime = clock();

	cout << res << endl;
	cout << "time: " << double(endTime - startTime) / CLOCKS_PER_SEC << " s" << endl;

	return 0;
}