1390. 四因数
题目链接:1390. 四因数
代码如下:
classSolution{public:intsumFourDivisors(vector<int>&nums){init();intres=0;for(intx:nums){if(divisor_num[x]==4){res+=divisor_sum[x];}}returnres;}private:constexprstaticintMX=100'001;intdivisor_num[MX];intdivisor_sum[MX];intinit(){for(inti=1;i<MX;i++){for(intj=i;j<MX;j+=i){//枚举i的倍数jdivisor_num[j]++;//i是j的因子divisor_sum[j]+=i;}}return0;}};