C + + two-dimensional arrays (double pointers as function Parameters)

The study content of this article reference: http://blog.csdn.net/yunyun1886358/article/details/5659851

http://blog.csdn.net/xudongdong99/article/details/6723163

1. Use a two-dimensional array as an example of formal parameters:

void func (int arr[][])  {    }  int  main () {      int array[] [ten];       Func (array);           // use a two-dimensional array to be an argument, call a function }

The above example can be compiled through, note, here must give the size of the second dimension , otherwise the compilation will not pass.

2. Use a one-dimensional pointer as a function parameter in the following form:

void func1 (int (*arr) [ten]) {}int  main () {    int array[] [ten];      Func1 (array);  }

This declaration is also ok, because the two-dimensional array name is a pointer to a one-dimensional array, in the same way, it must also indicate the size of the second dimension , otherwise the compilation will not pass.

3. Use double pointers as formal parameters: the parameters here specify the dimensions of each dimension of the two-dimensional array

voidFunc2 (int* * parr,intMintN) {}intmain () {intm =Ten; intn =Ten; int* * Parray =New int*[m]; parray[0] =New int[m * n];//Allocating contiguous memory//cannot be addressed with parray[1][0] and you need to specify the subscript addressing method     for(inti =1; I < m; i++) {parray[i]= parray[i-1] +n;  } func2 (parray, m, n); }  

4.Demo (from the race code NETWORK)

Question:

There are n squares, left-to-right in a row, numbered 1-n.

There are 3 types of operation for M operations:

1. Modify the weights of a lattice,

2. to seek a continuous lattice of weights and

3. Ask for the maximum value of a continuous lattice.

For each of the 2, 3 operation output you have to find the Results.

Input: Enter the first row of two integers, N for the number of squares, m for the number of operations, N and M in the middle with a space separated; Next Enter n lines, one integer per line representing the weights of a lattice Next enter M lines, each line has three integers, the middle is separated by a space; the first is the selected operation type 1-3, and the second and third integers are the number of the Operation Lattice.

Input Example: 7 · 7 8 9 2 1 3 3 1 3 2 1 2

Output: No output if 1 operation is performed Outputs an integer if the 2 and 3 operations are performed

Sample Output: 24 9 15

Solution: using a double pointer as an example of a function parameter, the argument in this example is a dynamically created Double-pointer form that can be passed directly as an argument, and if the argument is just a normal two-dimensional array, it is necessary to do the corresponding type conversion when doing the Argument.

#include <iostream>using namespacestd;//operation result output functionvoidOperatortype (intweight[],intNint**operatorarr,intM) {intsum =0; intmax=0; Switch(operatorarr[m][0])    {     case 1:         break;  case 2:             for(inti = operatorarr[m][1];i <= operatorarr[m][2];i++) {sum+ = weight[i-1]; } cout<< sum <<endl;  break;  case 3:         for(inti = operatorarr[m][1];i <= operatorarr[m][2];i++) {max=0.0; if(max < weight[i-1]) Max= weight[i-1]; } cout<< Max <<endl;  break; default:         break; }}intmain () {intn, m;//n means the number of squares m indicates the number of operationsCIN >> N >>m; int*weight =New int[n];//the weights of each lattice    int**oper =New int*[m];//an array of two-dimensional arrays that hold operands and grid numbers     for(inti =0; I < m;i++) {oper[i]=New int[3]; }     for(inti =0; I < N;i++)//weight of the input grid{cin>>weight[i]; }     for(inti =0; I < M;i++)//input Operation Array    {         for(intj =0; J <3; j + +) Cin>>oper[i][j]; }     for(inti =0; I < m;i++) {operatortype (weight, n, oper, i); } System ("Pause"); return 0;}

C + + two-dimensional arrays (double pointers as function Parameters)