The step jumping expansion problem of sword finger offer

Step jump expansion problem

Title Description ：
A frog can jump up at a time 1 Stepped steps , You can jump on it 2 level …… It can also jump on n level . Ask the frog to jump on one n Steps of steps (n As a positive integer ) How many jumps are there in total ？

Problem solving ：

f[0]=f[1]=1
f[n]=f[n-1]+f[n-2]+…+f[0]
because f[n-1]=f[n-2]+…+f[0]
therefore f[n]=2 * f[n-1]
Empathy f[n-1]=2 * f[n-2]
The resulting f[n]=2 * 2 * 2 * … * f[0]

Code ：

class Solution {
public:
    int jumpFloorII(int number) {
        if(number==1 || number==0){
            return 1;
        }
        int sum=1;
        // because 0 and 1 All are 1 So it doesn't matter where you start 
        for(int i=1;i<number;i++){
        // Left shift multiplication 2, Move right divided by 2
            sum=sum<<1;
        }
        return sum;
    }
};