Table of contents
1. In some cases, array variable names in C++ can be regarded as pointers.
2.C language scanf input statement, printf output statement
3. Use pointers as dynamic arrays
Otaru C++ multiple chapters ⑧ (3) Pointers and strings, (4) Functions and pointers
https://blog.csdn.net/weixin_44775255/article/details/129397866
1. In some cases, array variable names in C++ can be regarded as pointers.
#include<iostream>
using namespace std;
// 1.用数组名访问数组
int a[]={10,11,12,13,14,15};
int *p=a+1;
int main(){
cout<<*a<<endl; //默认输出第一个
cout<<*(a+2)<<endl;
cout<<*(++p)<<endl;
return 0;
}
- *a represents, initially pointing to the position a[0], which is 10.
- *(a+2) a+2 means that the address of array a is moved back 2 digits, which is the address of a[2], and the pointer points to 12.
- *p = a+1, then p points to the address of a[1], ++p points to the address of a[2], *(++p) is the value 12 of a[2].
- It can be found that the array variable a can be used as a pointer, pointing to the first array element by default!
- Pointers are dynamic data structures, and arrays are static data structures. Pointers are used in input statements in C language. Next, let’s learn about the input scanf and output printf of C language.
2.C language scanf input statement, printf output statement
Before using C language input and output, you must import the library: include<cstdio> //C language standard IO
Output format: printf ("format control string" , output list)
#include<iostream>
#include<cstdio>
using namespace std;
int main(){
// 输出用法例子
printf("整数：%d,长整数：%ld\n",100*1234,1+3*10000000);
printf("单精度：%f,双精度：%lf\n",1.5*1234,1+3*1.55);
printf("保留2位：%.2f, 9个占位并保留3位：%9.3f\n",3.14*1422,3.14159*3);
printf("字符:%c, 字符串:%s",'A',"abccd");
// 输入用法例子
int a;
double b;
float c;
scanf("%d%lf%f",&a,&b,&c);
printf("a=%d b=%lf c=%f",a,b,c);
return 0;
} 
scanf uses array name
//2.scanf使用数组名
#include<iostream>
#include<cstdio>
using namespace std;
int a[5];
int main(){
for(int i=0;i<5;i++){
scanf("%d",a+i); //a+i就是地址，a+0,a+1,a+4等地址
}
for(int i=0;i<5;i++){
// cout<<*(a+i)<<" ";
printf("a[%d]=%d\n",i,a[i]); //a[i]就是 *(a+i)
}
return 0;
}
3. Use pointers as dynamic arrays
What is a dynamic array? The length of the array space can be changed, not fixed.
Using pointers as arrays can achieve dynamic changes.
For example: Find the sum of array elements.
//3.指针也可以看成数组名
#include<iostream>
#include<cstdio>
using namespace std;
int n;
int *a; //指针变量a当数组名使用
int main(){
scanf("%d",&n);
//指针变成数组怎么写？
a = new int[n+1]; // 申请连续的n+1片的空间给指针a
for(int i=0;i<5;i++){ // 输入值到数组
scanf("%d",&a[i]);
}
for(int i=1;i<5;i++){ // 求和运算
a[i] = a[i] + a[i-1];
}
for(int i=0;i<5;i++){ // 输出结果
printf("%d ",a[i]);
}
return 0;
} 