[英]Using Vectors instead of Arrays
I have wrote a small program that generates unique random numbers. 我写了一个小程序,可以生成唯一的随机数。 I wrote it first using what I know, an array, to load and print the numbers. 我首先使用我所知道的数组(即数组)来加载和打印数字。 I am trying to replace the array with a vector so if I want make copies of the list I can do that easier. 我正在尝试用向量替换数组,因此,如果要复制列表,可以更轻松地完成。 I am getting a error. 我收到一个错误。
error: cannot convert 'std::vector<int>' to "std::vector<int>*' for argument '1' to bool numInList(std::vector<int>*, int)'
this error occurs when I call the numInList function. 当我调用numInList函数时,会发生此错误。
I am new at using vectors but I thought you could use vectors like arrays with the benefits of built in functions, no fixed size, and the ability to copy one vector into another vector. 我是使用向量的新手,但我认为您可以使用向量(如数组),因为它具有内置函数的优点,没有固定大小,并且能够将一个向量复制到另一个向量中。
here is my code: 这是我的代码:
#include <iostream>
#include <string>
#include <vector>
#include <fstream>
#include <cstdlib>
#include <ctime>
using namespace std;
bool numInList(vector <int> randNumbers[], int num);
const int length = 100;
int main()
{
int countCheck = 0;
vector <int> randNumbers(length);
vector <int> newlist();
srand(time(0));
while(countCheck < length){
int num = rand() % 90000 +10000;
if (!numInList(randNumbers, num)){
randNumbers[countCheck] = num;
cout << "The Random Number " << randNumbers[countCheck] << endl;
countCheck++;
}
}
cout << "\n\n\n";
newlist[] = randNumbers[];
return 0;
}
bool numInList(vector<int> randNumbers[], int num){
for (int index = 0; index < length; index++){
if (randNumbers[index] == num){
return true;
}
}
return false;
}
I tried de-referencing hoping that would solve the problem 我尝试取消引用,希望可以解决问题
if (!numInList(&randNumbers, num))
then I get an error on the IF statement in the function numInList 然后我在函数numInList中的IF语句上收到错误
error: ISO C++ forbids comparisons between pointers and integer [f-permissive]
Any help would be greatly appreciated. 任何帮助将不胜感激。
I have changed a few things, now I don't get any compilation errors but the program crashes when executed ... any suggestions??? 我更改了几件事,现在没有任何编译错误,但是执行时程序崩溃了……有什么建议???
#include <iostream>
#include <string>
#include <vector>
#include <fstream>
#include <cstdlib>
#include <ctime>
using namespace std;
bool numInList(vector <int> randNumbers, int num);
const int length = 100;
int main()
{
int countCheck = 0;
vector <int> randNumbers;
vector <int> newlist;
srand(time(0));
while(countCheck < length){
int num = rand() % 90000 +10000;
if (!numInList(randNumbers, num)){
randNumbers.push_back(num);
cout << "The Random Number " << randNumbers[countCheck] << endl;
countCheck++;
}
}
cout << "\n\n\n";
newlist = randNumbers;
return 0;
}
bool numInList(vector<int> randNumbers, int num){
for (int index = 0; index < length; index++){
if (randNumbers[index] == num){
return true;
}
}
return false;
}
You should pass vectors around by reference (unless you want to copy it). 您应该通过引用传递矢量(除非您要复制它)。 If you're not going to modify the vector, make it a const reference: 如果您不打算修改向量,请使其成为const引用:
bool numInList(const vector<int>& randNumbers, int num)
More info: How to pass objects to functions in C++? 更多信息: 如何将对象传递给C ++中的函数? (These are the very basics of C++. Get them right.) (这些是C ++的基本知识。正确使用它们。)
Also, you can use vector::size
to get the number of elements in a vector. 另外,您可以使用vector::size
获取向量中元素的数量。 This way index
will never exceed the size of the vector and you won't have an out-of-bounds access, no matter what the size of the vector is: 这样, index
将永远不会超出向量的大小,并且无论向量的大小是多少,您都将无法进行越界访问:
for (int index = 0; index < randNumbers.size(); index++)
Here, I rewrote the whole thing for you to show how a vector should be used. 在这里,我为您重写了整个内容,以显示应如何使用向量。 Read it through carefully and make sure you understand everything (including why your original approach was not the best possible design choice): 仔细阅读并确保您理解所有内容(包括为什么原始方法不是最佳的设计选择):
int main()
{
const int length = 100;
vector<int> randNumbers;
vector<int> newList;
srand(time(0));
while(randNumbers.size() < length){
int num = rand() % 90000 +10000;
if (!numInList(randNumbers, num)){
randNumbers.push_back(num);
cout << "The Random Number " << randNumbers.back() << endl;
}
}
cout << "\n\n\n";
newList = randNumbers;
return 0;
}
bool numInList(const vector<int>& randNumbers, int num){
for (int index = 0; index < randNumbers.size(); index++){
if (randNumbers[index] == num){
return true;
}
}
return false;
}
numInList vector randNumbers []的参数等效于vector * randNumbers将参数更改为
bool numInList(vector<int> &randNumbers, int num)
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