关于stract应用的问题求解

Question

以下问题在DEVC++中编译

#include<iostream>
#include<string.h> 
using namespace std;
int main()
{
    char str1[] = "I am ";
    char str2[] = "happy."; 
    cout<<str1<<endl<<str2<<endl;
        cout<<strcat(str1,str2);
    return 0;
}

如上程序的输出结果如下，会先正常的输出原本的str1和str2，在输出两者连接后的字符串

```c++
I am
happy.
I am happy.

但如果按照以下方式编写程序

#include<iostream>
#include<string.h>
using namespace std;
int main()
{
    char str1[] = "I am ";
    char str2[] = "happy."; 
    cout<<str1<<endl<<str2<<endl<<strcat(str1,str2);
    return 0;
}

则运行结果如下

I am happy.
happy.
I am happy.

求解原因

Answer 1

从右向左执行，从左到右输出