[C++] 每日一题：比特位个数

class Solution {public:  int count(int num) {    int n = 0;    while (num != 0) {      ++n;      num = (num & num-1);    }    return n;  }  vector<int> countBits(int num) {    vector<int> dp(num+1, 0);    for (int i = 0; i <= num; ++i) {      dp[i] = count(i);    }    return dp;  }};

class Solution {public:  vector<int> countBits(int num) {    vector<int> dp(num+1, 0);    for (int i = 1; i <= num; ++i) {      dp[i] = dp[i & (i-1)] + 1;    }    return dp;  }};