Cp

cp

//getNumberOfWaysToClimbStairs
An O(n) time and O(1) space solution:

	private static int getNumberOfWaysToClimbStairs(int n) {
		int a = 1, b = 2, c = 4, d = 0;

		if (n == 0 || n == 1 || n == 2)
			return n;
		if (n == 3)
			return c;

		for (int i = 0; i < n - 3; i++) {
			d = c + b + a;
			a = b;
			b = c;
			c = d;
		}
		return d;
	}
	
	
	
// lower case and upper case string fast input
inline void ins(string &s)
{
    string i="";
    int temp=getchar_unlocked();
    while((temp<'a'&& temp>'z') || (temp<'A' && temp>'Z'))
        temp=getchar_unlocked();
    while((temp>='a'&&temp<='z') || (temp>='A'&&temp<='Z'))
    {
        i+=(char)temp;
        temp=getchar_unlocked();
    }
    s = i;
}