8-1. Pointer 小考試

1. 某科技業筆試題

int a[] = {1,2,3,4,5,6};
int *p = a;

*(p++) += 100;
*(++p) += 100;

for ( int i = 0 ; i < 6 ; i++ )
    cout << a[i] << " ";

(a) 1 2 3 4 5 6

(b) 101 2 103 4 5 6

(c) 101 102 3 4 5 6

(d) 1 102 3 104 5 6

(e) 以上皆非

2. 進階筆試

int a[] = {1,2,3,4,5,6};
int *p = &a[3];
int *p2 = a+5;

*p = 100;
*p2 = *p2 - *p;

for ( int i = 0 ; i < 6 ; i++ )
    cout << a[i] << " ";

(a) 1 2 3 4 5 6

(b) 101 2 103 4 5 6

(c) 101 102 3 4 5 6

(d) 1 102 3 104 5 6

(e) 以上皆非 填充

3. 深度筆試

void swap( int a , int b ){
    int t = a;
    a = b;
    b = t;
}

int main(){
    int x = 3, y = 5;
    swap( x, y );
    cout<<"x = "<<x<<" ,y = "<<y;
}

要怎麼改，才能達到交換效果

4. 困難筆試

int a[] = {1,2,3,4,5,6};
int *p = &a[3];
int **pp = &p;

*pp = a;
*p  = 100;

for ( int i = 0 ; i < 6 ; i++ )
    cout << a[i] << " ";

(a) 100 2 3 4 5 6

(b) 1 100 3 4 5 6

(c) 1 2 3 4 5 6

(d) 1 2 100 4 5 6

(e) 1 2 3 100 5 6

解答：

1. (b) 101 2 103 4 5 6
2. (e) 以上皆非，正解是 1 2 3 100 5 -94

3. 答案

    void swap( int *a , int *b ){
        int t = *a;
        *a = *b;
        *b = t;
    }
   
    int main(){
        int x = 3, y = 5;
        swap( &x, &y );
        cout<<"x = "<<x<<" ,y = "<<y;
    }
   

4. (a) 100 2 3 4 5 6

自己實作一個printArray()的function

#include<bits/stdc++.h>
using namespace std;

void printArray(int *arr,int length){
   for(int i =0; i<length;i++){
        cout<<arr[i]<<" ";
   }
   return;
}

int main(){

    int N = 5; // 陣列長度
    int numbers[N];

    for(int i =0; i<N;i++){
        numbers[i]=i; //初始化
    }

    cout<<"numbers的記憶體address: "<<numbers<<endl;

    cout<<"numbers裡面的資料: ";
    printArray(numbers,N);
}