一、題目說明
題目338. Counting Bits,給定一個正整數n,返回從0-n之間所有數組對應二進制數包含1的個數。難度是Medium!複雜度要求是O(n)。
二、我的解答
這個題目用dp,其實是非常簡單的:
class Solution{
public:
vector<int> countBits(int num){
vector<int> res(num+1,0);
if(num>0) res[1]=1;
for(int i=2;i<=num;i++){
int tmp = i%2;
res[i] = res[i/2] + tmp;
}
return res;
}
};
性能如下:
Runtime: 52 ms, faster than 93.90% of C++ online submissions for Counting Bits.
Memory Usage: 9.6 MB, less than 63.42% of C++ online submissions for Counting Bits.
三、優化措施
無