雅可比迭代法

//  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
#include<iostream>

#include<cmath>

using namespace std;
double fanshu(double x[], double y[], int n)
{
    double sums = 0;
    for(int p = 0; p < n; p++)
        sums += (y[p] - x[p]) * (y[p] - x[p]);
    return sqrt(sums);
}
void main()
{
    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};
    double b[6] = {0, 5, -2, 5, -2, 6};
    double x[6] = {0, 0, 0, 0, 0, 0}; //设置X初值全为0；
    double y[6] = {0, 0, 0, 0, 0, 0};
    int N = 50;
    int k, i, j, l;
    double e;
    for(k = 0; k < N; k++)
    {
        for(i = 0; i < 6; i++)
        {
            double sum = 0;
            for(j = 0; j < 6; j++)
                if(j != i)
                {
                    sum += A[i][j] * x[j];
                }
            y[i] = (b[i] - sum) / A[i][i];
        }
        e = fanshu(x, y, 6);
        if(e < 0.0001)
        {
            break;
        }
        for(l = 0; l < 6; l++)
            x[l] = y[l];
    }
    cout << "迭代次数为：" << k << endl;
    cout << "结果为： ";
    for(int h = 0; h < 6; h++)
        cout << y[h] << " ";
    cout << endl;
}