1 //  如下程序中的for语句未修改前为：for(j=0;j!=i&&j<6;j++) ，输出结果为5次迭代而不是正确的27次，j!=i放在for语句中则会减少迭代次数从而产生误解 2 #include
     
       3  4 #include
      
        5  6 using namespace std; 7 double fanshu(double x[], double y[], int n) 8 { 9     double sums = 0;10     for(int p = 0; p < n; p++)11         sums += (y[p] - x[p]) * (y[p] - x[p]);12     return sqrt(sums);13 }14 void main()15 {16     double A[6][6] = {
   4, -1, 0, -1, 0, 0, -1, 4, -1, 0, -1, 0, 0, -1, 4, -1, 0, -1, -1, 0, -1, 4, -1, 0, 0, -1, 0, -1, 4, -1, 0, 0, -1, 0, -1, 4};17     double b[6] = {
   0, 5, -2, 5, -2, 6};18     double x[6] = {
   0, 0, 0, 0, 0, 0}; //设置X初值全为0；19     double y[6] = {
   0, 0, 0, 0, 0, 0};20     int N = 50;21     int k, i, j, l;22     double e;23     for(k = 0; k < N; k++)24     {25         for(i = 0; i < 6; i++)26         {27             double sum = 0;28             for(j = 0; j < 6; j++)29                 if(j != i)30                 {31                     sum += A[i][j] * x[j];32                 }33             y[i] = (b[i] - sum) / A[i][i];34         }35         e = fanshu(x, y, 6);36         if(e < 0.0001)37         {38             break;39         }40         for(l = 0; l < 6; l++)41             x[l] = y[l];42     }43     cout << "迭代次数为：" << k << endl;44     cout << "结果为： ";45     for(int h = 0; h < 6; h++)46         cout << y[h] << " ";47     cout << endl;48 }