Question

C++中<cmath>和<cstdlib>

请教各位大虾： C++中<cmath>和<cstdlib> 是否都包含 srand()和rand() 函数，怎么有的程序，将<cstdlib>改成<cmath>也可以。
#include <iostream>
#include <ctime>
#include <cmath> //那为什么写<cmath>不写＜cstdlib＞也可以运行同样效果
using namespace std;

int main()
{
int correctCount = 0;
int count = 0;
long startTime = time(0);

while (count < 10)
{
srand(time(0));
int number1 = rand() % 10;
int number2 = rand() % 10;

if (number1 < number2)
{
int temp = number1;
number1 = number2;
number2 = temp;
}

cout << "What is " << number1 << " - " << number2 << "? ";
int answer;
cin >> answer;

if (number1 - number2 == answer)
{
cout << "You are correct!\n";
correctCount++;
}
else
cout << "Your answer is wrong.\n" << number1 << " - " << number2 << " should be " << (number1 - number2) << endl;

count++;
}
long endTime = time(0);
long testTime = endTime - startTime;

cout << "Correct count is " << correctCount << "\nTest time is " << testTime << " seconds\n";

return 0;
}

Answer 1

这是由于你包含了iostream,包含了iostream后就可以不再包含stdlib.h而使用里面声明的函数了

***********************************************************

这两个函数的声明在stdlib.h中,在C++中可以通过包含cstdlib现实,math.h中没有.

Answer 2

srand()和rand()在<cstdlib>中