模板题链接
1 #include <bits/stdc++.h>
2 using namespace std;
3
4 const int N = 110;
5 const double eps = 1e-6;
6 int n;
7 double a[N][N];
8
9 int solve()
10 {
11 int c, r;
12 for (c = 0, r = 0; c < n; c ++ )
13 {
14 int t = r;
15 for (int i = r; i < n; i ++ ) // 找到绝对值最大的行
16 if (fabs(a[i][c]) > fabs(a[t][c]))
17 t = i;
18
19 if (fabs(a[t][c]) < eps) continue;
20
21 for (int i = c; i <= n; i ++ ) swap(a[t][i], a[r][i]); // 将绝对值最大的行换到最顶端
22 for (int i = n; i >= c; i -- ) a[r][i] /= a[r][c]; // 将当前行的首位变成1
23 for (int i = r + 1; i < n; i ++ ) // 用当前行将下面所有的列消成0
24 if (fabs(a[i][c]) > eps)
25 for (int j = n; j >= c; j -- )
26 a[i][j] -= a[r][j] * a[i][c];
27
28 r ++ ;
29 }
30
31 if (r < n)
32 {
33 for (int i = r; i < n; i ++ )
34 if (fabs(a[i][n]) > eps)
35 return 2; // 无解
36 return 1; // 有无穷多组解
37 }
38
39 for (int i = n - 1; i >= 0; i -- )
40 for (int j = i + 1; j < n; j ++ )
41 a[i][n] -= a[i][j] * a[j][n];
42
43 return 0; // 有唯一解
44 }
45
46 signed main(){
47 cin >> n;
48 for(int i = 0; i < n; ++i){
49 for(int j = 0; j < n + 1;++j){
50 cin >> a[i][j];
51 }
52 }
53
54 int ans = solve();
55 if(ans == 0){
56 for(int i = 0; i < n; ++i) printf("%.2f\n", a[i][n]);
57 }else ...
58
59 return 0;
60 }
