c++ - 除非所有字段都初始化为 0，否则 int 数组会给出疯狂的值，为什么？

Question

int TwoThrows();


int main(){

        int Throws, Throw, Frequency[13]={0,0,0,0,0,0,0,0,0,0,0,0,0};
        randomize();


        cout << "\nThis program simulates throws of two dice.";
        cout << "\n\nHow many throws : ";
        cin >> Throws;



        // Calls TwoThrows and saves in Frequency by value
        for(int I=0; I<Throws; I++){
                Throw=TwoThrows();   //2-12
                Frequency[Throw]++;   //2-12

        }

         // Prints array:
        for(int I=0; I<11; I++){
                cout << I+2 << ":\t" << Frequency[I+2] << "\n";

        }

        return 0;
}

int TwoThrows(){
        unsigned int I=(random(6)+1)+(random(6)+1);

        return I;

}

这打印:

2: 13173:27244:41455:55136:70567: 83438: 69829:558010:417611: 277612: 1388

太好了。

但是，我想知道的是，为什么我必须将数组设置为{0,0,0,0,0,0,0,0,0,0,0,0,0}？

如果我不这样做；我得到:

2:306268683:16382334:8445452955:16:97:42025108: 41991979: 84455575710:311:420257412: 2130567168

Answer 1

如果您不初始化数组，然后继续递增其元素，技术上这是 undefined behaviour .

实际发生的情况是，当 main() 启动时，数组的元素会获取恰好在堆栈上的任何值。