矩形覆盖-避免递归

public class Solution {
public int RectCover(int target) {
if(target<=0) return 0;
else if(target<=2) return target;
else {
int a = 1,b = 2,c = 0;
for(int i=3;i<=target;i++){
c = a+b;
a = b;
b = c;
}
return c;
}
}
}