我要求用户输入大小和数组，但是当我打印矢量时，它仅显示"0"作为输出 [英] I am asking user to enter the size and array but when I am printing the vector it shows '0' only as output

问题描述

我声明了一个向量，并试图放入大小和值并打印出来

I declared a vector and trying to put size and values and printing it

#include<iostream>
#include<vector>
using namespace std;
int main()
{
    int s;          
    cin>>s;                   //taking size of vector
    vector <int> arr(s);
    int input;
    while (cin >> input)
       {arr.push_back(input);}     //inserting the values in array
    for(int i=0;i<s;i++)
        cout<<" "<<arr[i];         //printing the values
}

我的输入5

1 2 3 4 5

1 2 3 4 5

预期产量

1 2 3 4 5

1 2 3 4 5

电流输出0 0 0 0 0

Current output 0 0 0 0 0

推荐答案

此行:

vector <int> arr(s);

使 arr 的大小为 s .它将具有已默认初始化为0的 s 个元素.然后您对该向量进行 push_back ，这会将 additional 元素添加到向量.

makes arr have the size s. It will have s elements that have been default-initialized to 0. Then you are doing push_back on this vector, which adds additional elements into the vector.

当打印出第一个 s 元素时，您看不到从 cin 读取的值，但看到的是 s 个在 arr 的声明中创建的初始值.

When you print out the first s elements, you are not seeing the values that were read from cin, but the s number of initial values created in the declaration of arr.

要解决此问题，要么在声明 arr 时不给出大小，要么仅使用 arr [i] = input; 而不是 push_back().

To fix this, either don't give a size when you declare arr, or else just use arr[i] = input; instead of push_back() in the loop.

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