1 #include <iostream>
2 #include <cstdio>
3 #include <math.h>
4 #include <time.h>
5 #include <stdlib.h>
6 using namespace std;
7 const int MAXN = 10000;
8 double a[MAXN][MAXN];
9 double b[MAXN];
10 double x[MAXN];
11 int main()
12 {
13 int n=3;
14 double l;
15 int i,number;
16 double sum;
17 srand((unsigned) time(NULL));
18 printf("a[][]:\n");
19 for(int i = 0;i<n;i++){
20 for(int j = 0;j<n;j++){
21 number = rand() % 11;
22 a[i][j]=(double)(number*1.131121);
23 printf("%f ",a[i][j]);
24 sum+=a[i][j];
25 }
26 cout << endl;
27 b[i]=sum;
28 sum=0;
29 }
30 ///消元过程
31 for(int k = 0;k<n-1;k++){///消元行
32 for(int i = k+1;i<n;i++){///被消元行
33 l = a[i][k]/a[k][k];
34 for(int j = k;j<n;j++){
35 a[i][j]-=l*a[k][j];
36 }
37 b[i]-=b[k]*l;
38 }
39 }
40 ///回带过程
41 for(int i = n-1;i>=0;i--){
42 x[i] = b[i];
43 for(int j = n-1;j>i;j--){
44 x[i] -= a[i][j]*x[j];
45 }
46 x[i] /= a[i][i];
47 }
48 ///高斯消元法输出
49 printf("x[]:(gaussi)\n");
50 for(int i = 0;i<n;i++){
51 printf("%.6f ",x[i]);
52 }
53 cout << endl;
54
55 //-------------------------
56
57 double maxs;
58 ///消元过程
59 for(int k = 0;k<n-1;k++){///消元行
60 int cur = k;
61 maxs = fabs(a[k][k]);
62 for(int i = k;i<n;i++)if(maxs<fabs(a[i][k])){maxs = fabs(a[i][k]);cur = i;}///选主元
63 if(cur != k){
64 double temp;
65 for(int j = k;j<n;j++){
66 temp = a[k][j];
67 a[k][j] = a[cur][j];
68 a[cur][j] = temp;
69 }
70 temp = b[k];b[k] = b[cur];b[cur] = temp;
71 }
72
73 for(int i = k+1;i<n;i++){///被消元行
74 l = a[i][k]/a[k][k];
75 for(int j = k;j<n;j++){
76 a[i][j]-=l*a[k][j];
77 }
78 b[i]-=b[k]*l;
79 }
80 }
81
82 ///回带过程
83 for(int i = n-1;i>=0;i--){
84 x[i] = b[i];
85 for(int j = n-1;j>i;j--){
86 x[i] -= a[i][j]*x[j];
87 }
88 x[i] /= a[i][i];
89 }
90 ///高斯列主元素消元法输出
91 printf("x[]:(gaussi_row)\n");
92 for(int i = 0;i<n;i++){
93 printf("%.6f ",x[i]);
94 }
95 cout << endl;
96 return 0;
97 }
