printf函数需要包含库stdio.h

#include<stdio.h>

 printf("%f\n",vf[i]);

#include<vector>
#include<stdio.h>
//TODO: Use the standard namespace
using namespace std;
int main() {
    
    //declare and define a vector with values
    //        {5.0, 5.0, 5.0} and print 
    //         the vector to the terminal using cout
    // Hint: the syntax vector<datatype> varname(length, value) might help
vector<float> vf(4,5.0);
    // Use push back to add the values 3.0, 2.5, 1.4 
    //      to the back of the vector
vf.push_back(3.0);
vf.push_back(2.5);
vf.push_back(1.4);
    // Part 3: Print out the vector again using cout
for (int i = 0;i<vf.size();i++)
{    
//cout<<vf[i]<<endl;
printf("%f\n",vf[i]);
}
    //Use the vector assign method to override the current vector. 
    // The overriden vector should have 3 elements with 
    // the values {5.0, 5.0, 5.0}
vector<float> vf3(3,5.0);
printf("%s\n","-----------------------------------");

vf.assign(vf3.begin(),vf3.begin()+3);
int size2 = vf.size();
for(int i=0;i<size2;i++)
{
  // cout<<vf[i]<<endl;
   printf("%f\n",vf[i]);
}
 

    return 0;
}