矩形覆盖

public class Solution {
    public int RectCover(int target) {
        if(target <= 0)
            return 0;
        if(target == 1)
            return 1;
        if(target == 2)
            return 2;
        return RectCover(target-1) + RectCover(target-2);
    }
}

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