使用向量的C++程序

Question

我在這裏很難找到問題，程序必須讀取數字N，然後讀取N長度爲2的向量，將第一個向量的每個數字與第二個向量的相關數字相乘，然後減去每個先前的乘法（示例A [0] * B [0] - A [1] * B [1] .... A [N-1] * B [N-1]）任何答覆將不勝感激。 輸入值：3/ 1 2 -3 /4 -5 -6 輸出：-4 下面的代碼：

#include <iostream> 
#include <string> 
#include <sstream> 
#include <vector> 
#include <cstdlib> 

using namespace std; 

/* Splits string using whitespace as delimeter */ 
void split_input(vector<double> &vector_values, const string &input) 
{ 
    char delim = ' '; 

    stringstream mySstream(input); 

    string temp; 

    while(getline(mySstream, temp, delim)) 
    { 
     vector_values.push_back(atof(temp.c_str())); 
    } 
} 

double multiply(vector<double> &first_vector, vector<double> &second_vector) 
{ 
    double result = 0; 

    for(int i = 0; i < first_vector.size(); i++) 
    { 
     if (i == 0) 
     { 
      result = first_vector[i]*second_vector[i]; 
     } 
     else 
     { 
      result -= first_vector[i]*second_vector[i]; 
     } 
     cout << result << endl; 
    } 

    return result; 
} 


int main() 
{ 
    vector<double> first_vector; 
    vector<double> second_vector; 
    int num; 
    string input_values; 

    cout << "Please enter a number: " << endl; 
    cin >> num ; 

    /* Ignores the endline char from the previous cin */ 
    cin.ignore(); 

    /* Read first string, split it and store the values in a vector */ 
    getline(cin, input_values); 
    split_input(first_vector, input_values); 

    cin.ignore(); 

    /* Read second string, split it and store the values in a vector */ 
    getline(cin, input_values); 
    split_input(second_vector, input_values); 


    /* Multiply vectors */ 
    cout << multiply(first_vector, second_vector) << endl; 

    return 0; 
} 

Answer 1

split_input(first_vector, input_values);後刪除cin.ignore()。 cin.ignore()第二個向量的第一個元素總是0。您的main()應該看起來像這樣：

int main() 
{ 
    vector<double> first_vector; 
    vector<double> second_vector; 
    int num; 
    string input_values; 

    cout << "Please enter a number: " << endl; 
    cin >> num ; 

    /* Ignores the endline char from the previous cin */ 
    cin.ignore(); 

    /* Read first string, split it and store the values in a vector */ 
    getline(cin, input_values); 
    split_input(first_vector, input_values); 

    // following line causes the first element of the second vector to become 0 
    // cin.ignore(); 

    /* Read second string, split it and store the values in a vector */ 
    getline(cin, input_values); 
    split_input(second_vector, input_values); 


    /* Multiply vectors */ 
    cout << multiply(first_vector, second_vector) << endl; 

    return 0; 
}