C++ cout 不显示任何内容

问题描述

什么可以解释为什么 cout 在这段代码中没有显示任何内容?我知道它与行 v[0] = 1; 有关.但我不知道为什么，有人对此有解释吗?

What may explain why the cout is not displaying anything in this code? I know it's related to the line v[0] = 1; but I can't find out why, does someone have an explanation for it?

我也知道改变 v[0] = 1;对于 v.push_back(1);就能解决问题.

I also know that changing v[0] = 1; for v.push_back(1); would solve the problem.

#include <iostream>
#include <vector>

using namespace std;

int main()
{
    vector<int> v;
    v[0] = 1;
    cout << "Hello" << endl;
    return 0;
}

推荐答案

你不能做 v[0]=1 因为你还没说向量 v 有多少个元素代码> 有.所以它会导致运行时错误(它崩溃)

You cannot do v[0]=1 because you haven't said how many elements the vector v has. So it causes run time error(it crashes)

将其声明为 vectorv(10)(这表示 v 将有 10 个元素)并使用 v[0]=1

Declare it as vector<int>v(10) (this says that v will have 10 elements)and use v[0]=1

或

如果您事先不知道矢量大小，请使用 v.push_back(1);

If you don't know the vector size beforehand use v.push_back(1);

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