C++ LeetCode1780判断数字是否可以表示成三的幂的和

vector<int> three(1, 1);  // 初始值是1个1
while (three.back() < n) {
    three.push_back(three.back() * 3);
}

int num = three.size(), to = 1 << num;
for (int state = 0; state < to; state++) {
    int s = 0;
    for (int j = 0; j < num; j++) {
        if (state & (1 << j)) {
            s += three[j];
        }
    }
    if (s == n)
        return true;
}
return false;

class Solution {
public:
    bool checkPowersOfThree(int n) {
        vector<int> three(1, 1);
        while (three.back() < n) {
            three.push_back(three.back() * 3);
        }
        int num = three.size(), to = 1 << num;
        for (int state = 0; state < to; state++) {
            int s = 0;
            for (int j = 0; j < num; j++) {
                if (state & (1 << j)) {
                    s += three[j];
                }
            }
            if (s == n)
                return true;
        }
        return false;
    }
};

class Solution {
public:
    bool checkPowersOfThree(int n) {
        while (n) {
            if (n % 3 == 2)
                return false;
            n /= 3;
        }
        return true;
    }
};