#include<iostream>#include<math.h>#include<fstream>#include<stdlib.h>using namespace std;void print(double (*pArray)[4], int iWidth,int iHigh);void main(){  int n,m;  double a[3][4] = {    {100, 10, 1, 10},    {400, 20, 1, 20},    {900, 30, 1, 10},  };//第四列是增廣矩陣  int i,j;  n = 3;  cout<<"輸入方程組介數(shù)：";  cout<<n<<endl;  cout<<"輸入增廣矩陣："<<endl;  for(i = 0; i < n; i++){    for(j = 0; j < n + 1;j++){      cout<<a[i][j]<<"  ";    }    cout<<endl;  }  for(j = 0; j < n; j++){    double max = 0;    double imax = 0;    for(i = j; i < n; i++){      if(imax < fabs(a[i][j])){        imax = fabs(a[i][j]);        max = a[i][j];//得到各行中所在列最大元素        m = i;      }    }    if(fabs(a[j][j]) != max) {      double b = 0;      for(int k = j;k < n + 1; k++){        b = a[j][k];        a[j][k] = a[m][k];        a[m][k] = b;      }    }    print(a, 3, 4);    for(int r = j;r < n + 1;r++){      a[j][r] = a[j][r] / max;//讓該行的所在列除以所在列的第一個元素，目的是讓首元素為1    }    print(a, 3, 4);    for(i = j + 1;i < n; i++){      double c = a[i][j];      if(c == 0) continue;      for(int s = j;s < n + 1;s++){        double tempdata = a[i][s];        a[i][s] = a[i][s] - a[j][s] * c;//前后行數(shù)相減，使下一行或者上一行的首元素為0        print(a, 3, 4);      }      print(a, 3, 4);    }    print(a, 3, 4);  }  for(i = n - 2; i >= 0; i--){    for(j = i + 1;j < n; j++){      double tempData = a[i][j];      double data1 = a[i][n];      double data2 = a[j][n];      a[i][n] = a[i][n] - a[j][n] * a[i][j];      print(a, 3, 4);    }  }  print(a, 3, 4);  cout<<"方程組的解是："<<endl;  for(int k = 0; k < n; k++){    cout<<"x"<<k<<" = "<<a[k][n]<<endl;  }}void print(double (*pArray)[4], int iWidth,int iHigh) {  std::cout<<"Array: "<<"/n";  for(int i = 0; i < iWidth; i++){    for(int j = 0; j < iHigh;j++){      cout<<pArray[i][j]<<"  ";    }    cout<<endl;  }}