LeetCode-600.不含连续1的非负整数

题目：

代码：

class Solution {
public:
    int fib(int n) {
    if (n <= 0) return 1;
    if (n == 1) return 2;
    int a = 1;
    int b = 2;
    int c = 3;
    int i = n - 2;
    while(i--) {
        a = b;
        b = c;
        c = a + b;
    }
    
    return c;
}

int findIntegers(int num) {
    if (num == 0) return 1;
    if (num == 1) return 2;
    int nbits = 0;
    while(num>>nbits) {
        ++nbits;
    }
    
    if (num>>(nbits - 2) == 3) {
        return fib(nbits);
    } else {
        int mask = (1 << (nbits - 1)) - 1;
        return fib(nbits - 1) + findIntegers(num & mask);
    }
}
};

额外结论：