C++如何实现输入一个任意正整数后,当选择3时,电脑显示第三 位数位上...答:include <iostream> using namespace std;int main(){ int n,k,i,a[10]={1,10,100,1000,10000,100000,1000000,10000000,100000000,1000000000};cin>>n>>k;for(i=0; a[i]<=n; i++);if(i<k){cout<<"Error!"<<endl;return 0;} for(;k;k--)i--;cout<<n/a[i]%10<<endl;...