如何传递一个向量到函数？ [英] How to pass a vector to a function?

问题描述

我试图发送一个向量作为参数到一个函数，我不知道如何使它的工作。尝试了一堆不同的方式，但他们都给出不同的错误消息。
我只包括部分代码，因为它只有这一部分不工作。
（向量random随机填充，但排序，值介于0和200之间）

更新代码：

  #include< iostream> 
 #include< ctime> 
 #include< algorithm> 
 #include< vector> 
 
 using namespace std; 
 
 int binarySearch（int first，int last，int search4，vector< int>& random） 
 
 int main（）
 {
 vector< int>随机（100）; 
 
 int search4，found; 
 int first = 0; 
 int last = 99; 
 
 found = binarySearch（first，last，search4，random）; 
 
系统（pause）; 
 return（0）; 
} 
 
 int binarySearch（int first，int last，int search4，vector< int>& random）
 {
 do 
 {
 int mid =（first + last）/ 2; 
 if（search4> random [mid]）
 first = mid + 1; 
 else if（search4< random [mid]）
 last = mid  -  1; 
 else 
 return mid; 
} while（first< = last）; 
 
 return  - （first + 1）; 
} 
  

解决方案

将向量 c>作为引用或作为指针传递（我忽略了通过值传递它的选项，这显然是不希望的）。

作为参考：

  int binarySearch（int first，int last，int search4，vector< int> ; random）; 
 
 vector< int>随机（100）; 
 // ... 
 found = binarySearch（first，last，search4，random）; 
  

作为指针：

  int binarySearch（int first，int last，int search4，vector< int> * random）; 
 
 vector< int>随机（100）; 
 // ... 
 found = binarySearch（first，last，search4，& random）; 
  

内部 binarySearch 。或 - >

1. > binarySearch 期望一个向量< int> * ，但你传递一个向量< int> ; （在之前缺少和之后）


2. 在使用之前，不要取消引用 binarySearch 中的指针（例如， random [mid] （* random）[mid]


3. 您缺少 using namespace std; < include> s


4. 您分配给的第一个值和最后是错误的（应为0和99而不是 random [0] random [99]

I'm trying to send a vector as an argument to a function and i can't figure out how to make it work. Tried a bunch of different ways but they all give different error messages. I only include part of the code, since it's only this part that doesn't work. (the vector "random" is filled with random, but sorted, values between 0 and 200)

Updated the code:

#include <iostream>     
#include <ctime>        
#include <algorithm>    
#include <vector>       

using namespace std;

int binarySearch(int first, int last, int search4, vector<int>& random);

int main()
{
    vector<int> random(100);

    int search4, found;
    int first = 0;
    int last = 99;

    found = binarySearch(first, last, search4, random);

    system("pause");    
    return(0);      
}

int binarySearch(int first, int last, int search4, vector<int>& random)
{
    do
    {
        int mid = (first + last) / 2;  
        if (search4 > random[mid]) 
            first = mid + 1;  
        else if (search4 < random[mid]) 
            last = mid - 1; 
        else
            return mid;     
    } while (first <= last); 

    return -(first + 1);
}

解决方案

It depends on if you want to pass the vector as a reference or as a pointer (I am disregarding the option of passing it by value as clearly undesirable).

As a reference:

int binarySearch(int first, int last, int search4, vector<int>& random);

vector<int> random(100);
// ...
found = binarySearch(first, last, search4, random);

As a pointer:

int binarySearch(int first, int last, int search4, vector<int>* random);

vector<int> random(100);
// ...
found = binarySearch(first, last, search4, &random);

Inside binarySearch, you will need to use . or -> to access the members of random correspondingly.

Issues with your current code

1. binarySearch expects a vector<int>*, but you pass in a vector<int> (missing a & before random)
2. You do not dereference the pointer inside binarySearch before using it (for example, random[mid] should be (*random)[mid]
3. You are missing using namespace std; after the <include>s
4. The values you assign to first and last are wrong (should be 0 and 99 instead of random[0] and random[99]

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