每日一题 338. 比特位计数

338. 比特位计数

难点是发现规律

class Solution {
public:
    vector<int> countBits(int n) {
        
        vector<int> dp(n+1,0);
        if(n <=0)
        {
            return dp;
        }
        dp[1] = 1;
        if(n == 1)
        {
            return dp;
        }
        int bin = 0;
        for(int i=2;i<=n;++i)
        {
            int base = getBinary(i);
            dp[i] = dp[i-(1<<base)] + 1; 
        }
        return dp;
    }

    int getBinary(int num)
    {
        int ret = 0;
        while( num != 0)
        {
            num  = num >> 1;
            ++ret;
        }
        return ret-1;
    }
};