嘗試使用數組創建隨機數生成器並獲取標識符“i”是未定義的。 任何人都可以看到問題嗎？

Question

嘗試使用數組創建隨機數生成器，但“ a[i] = rand() ;” 我的代碼的一部分創建了“標識符 i 未定義”類型的錯誤。 誰能找到我在這里出錯的地方？ 謝謝

#include <iostream>
#include <string>
#include <array>

using namespace std;


int main()
{
    int a[10] = {};  
  
   
    for (int i = 0; i < size(a); i++); {

        a[i] = rand();

    }

    for (int i = 0; i < size(a); i++) {

        cout << "The random number is: " << a[i] << endl;

    }
    
}

Answer 1

$ clang++-7 -pthread -std=c++17 -o main main.cpp
main.cpp:15:11: error: use of undeclared identifier 'i'
        a[i] = rand();
          ^
main.cpp:13:38: warning: for loop has empty body
      [-Wempty-body]
    for (int i = 0; i < size(a); i++); {
                                     ^
main.cpp:13:38: note: put the semicolon on a separate line
      to silence this warning
1 warning and 1 error generated.
compiler exit status 1

clang 有用地指出您在 for 循環后有一個意外的分號。

Answer 2

您的代碼中的錯誤是一個雜散的分號。 嘗試學習 gdb 之類的調試器，將有助於解決此類問題。 rand()函數使用種子， srand()用於更改/設置種子。

#include <iostream>
#include <string>
#include <array>
#include <ctime>. // Added for random seed generation

using namespace std;


int main()
{
    int a[10] = {};  
  
    srand(time(0)); /* Added this to ensure seed of rand() is always different otherwise you might have ended up with same random numbers on different runs */
    
    for (int i = 0; i < size(a); i++) {   /*Issue was here, you had stray semicolon */

        a[i] = rand();

    }

    for (int i = 0; i < size(a); i++) {

        cout << "The random number is: " << a[i] << endl;

    }
    
}