剑指Offer之跳台阶

1 public int JumpFloor(int target) {    
2         if(target==1)
3             return 1;
4         else if(target==2)
5             return 2;
6         else
7             return JumpFloor(target-1)+JumpFloor(target-2);
8     }

 1 public int JumpFloor(int target) {    
 2         int a=1,b=2;
 3         int c=0;
 4         if(target==1)
 5             return 1;
 6         else if(target==2)
 7             return 2;
 8         for(int i=3;i<=target;i++) {
 9             c=a+b;
10             a=b;
11             b=c;
12         }
13         return c;
14     }