编程1
public static boolean isCan(int[] a, int n) {
        int len = a.length;
        int c = a[0] == 0 ? 1 : 0;
        int count = 0;
        for (int i = 1; i < a.length; i++) {
            if (a[i] == 1) {
                if (c > 2) {
                    count += (c - 1) / 2;
                    c = 0;
                }
            } else {
                c++;
            }
            if (count >= n) {
                return true;
            }
        }
        return false;
    }
编程2
    public static int perfectBag(int n, int a[]) {
        int[] f = new int[n + 1];
        f[0] = 1;
        for (int i = 0; i < a.length; i++) {
            for (int j = a[i]; j <= n; j++) {
                f[j] += f[j - a[i]];
            }
        }
        return f[n];
    }