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<iostream>
3
4 #include<cmath>
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 }
