c++常见操作的模板

1.统计时间

#include<ctime>
clock_t startTime = clock();
code();
clock_t endTime = clock();
cout << endl<< "time: " << double(endTime - startTime) / CLOCKS_PER_SEC << " s"<<endl;

2.读取文件

#include<iostream>
#include<fstream>
#include<cstdlib>
const int SIZE=60; 
int main()
{
	using namespace std;
	char filename[SIZE]="information.txt";
	ifstream inFile;
	inFile.open(filename);
	if(!inFile.is_open())
	{
		cout<<"Could not open the file"<<filename<<endl;
		cout<<"Program terminating.
";
		exit(EXIT_FAILURE);
	}
	double value;                                                                    //1
	double sum=0.0;
	int count=0;
 
    inFile>>value;                                                                     //1
    while(inFile.good())
    {
    	++count;
    	sum=sum+value;
    	inFile>>value;
    }
    if(inFile.eof())
    cout<<"end of file reached.
";
	else if(inFile.fail())
	cout<<"input terminated by data mismatch.
";
	else
	cout<<"input terminated for unknown reason.
";
	if(count==0)
	cout<<"NO DATA PROCESSED.
";
	else{
		cout<<"items read:"<<count<<endl;
		cout<<"sum:"<<sum<<endl;
	}
	inFile.close();       
     return 0;
}

3.写入文件

#incluede<fstream>
ofstream outFile;
outFile.open("carinfa.txt");        //要放入的文件名
outFile<<...                        //放入的信息
.
.
.
outFile.close();                    //关闭文件

4.产生0~89之间的随机数

#include<iostream>
#include<cstdlib>
#include<ctime>
using namespace std;
int main()
{
	double target;
	srand(time(0));
	for(int i=0;i<=20;i++)
	{
	target=rand()%90;
	cout<<target<<endl;
	}
	return 0;
}

6.传二维数组

int show(double* A,int row,int col)
{
    int i,j;
    double** B=new double*[col];
    for(i=0;i<row;i++)
    {
       B[i]=new double[col];
     }
    for(i=0;i<row;i++)
    {
        for(j=0;j<col;j++)
        {
           B[i][j]=*(A+i*col+j);
           cout<<B[i][j]<<"  ";
        }
        cout<<endl;
     }
     for(i=0;i<row;i++)
     {
        delete[] B[i];
     }
     delete[] B;
 }
//调用： show(A[0],4,7);