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.\n";exit(EXIT_FAILURE);}double value;                                                                    //1double sum=0.0;int count=0;inFile>>value;                                                                     //1while(inFile.good()){++count;sum=sum+value;inFile>>value;}if(inFile.eof())cout<<"end of file reached.\n";else if(inFile.fail())cout<<"input terminated by data mismatch.\n";elsecout<<"input terminated for unknown reason.\n";if(count==0)cout<<"NO DATA PROCESSED.\n";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);