C + +--dynamic array

Source: Internet
Author: User

first, about the use of arrays , there are several special places to note:

1. One-dimensional array name can be used as a pointer

Application: A one-dimensional array/two-dimensional array of arguments (see blog "C + +--two-D array parameter passing Http://www.cnblogs.com/cygalaxy/p/6963789.html")

2. Dynamic arrays

specific application: According to the actual need for an array to open the specific size.

int*p;//declares the dynamic array p as a global variable, and determines the actual length within the functionintMain () {intA=5; P=New int(A *sizeof(int));//Open 5 int element space for dynamic array P     for(intI=0;i<5;++i) {P[i]=i*2; P[i] equivalent to * (p+i) cout<<p[i]<<" "; } cout<<Endl; return 0;}

Operation Result:

0 2 4) 6 8

Two, several dynamic array Introduction:

1. Using STL Vector<t>, convenient, no need to consider open space

2. Using the pointer, as shown above, first declare a pointer, and then use new (in C language with malloc) to request the actual memory.

3.c++primer5 in the section describing arrays explicitly states that declaring an array cannot use a variable, as detailed below:

 int  a=5   int  arr[a]={0 , 1 , 2 , 3     , 4 }; //  error, A is not a constant  const  int  b= ; int  arr1[b]={0 , 1 , 2 , 3  , 4 }; //  correct, B is constant  

But some compilers can do this, and it could be a compiler extension!

C + +--dynamic array

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