高斯消元求调 60pts

Daniel_yao @ 2024-07-17 18:31:34

#include<bits/stdc++.h>
#define ll long long
#define For(i,l,r) for(int i=l;i<=r;++i)
#define FOR(i,r,l) for(int i=r;i>=l;--i)
#define eqs 1e-10

using namespace std;

const int N = 105;

int n;

double a[N][N];

signed main() {
  ios::sync_with_stdio(0);
  cin.tie(0), cout.tie(0);
  cin >> n;
  For(i,1,n) {
    For(j,1,n+1) {
      cin >> a[i][j];
    }
  }
  for (int i = 1; i <= n - 1; ++i) {
    For(j,i+1,n) if(fabs(a[i][i]) < fabs(a[j][i])) swap(a[i], a[j]);
    if(fabs(a[i][i]) < eqs) continue;
    For(j,i+1,n) {
      double w = a[j][i] / a[i][i];
      For(l,i,n+1) {
        a[j][l] -= w * a[i][l];
      }
    }
  }
  for (int i = n; i >= 2; --i) {
    if(fabs(a[i][i]) < eqs) continue;
    FOR(j,i-1,1) {
      double w = a[j][i] / a[i][i];
      For(l,i,n+1) {
        a[j][l] -= w * a[i][l];
      }
    }
  }
  For(i,1,n) if(fabs(a[i][i]) < eqs && fabs(a[i][n+1]) > eqs) return puts("-1"), 0; 
  For(i,1,n) if(fabs(a[i][i]) < eqs && fabs(a[i][n+1]) < eqs) return puts("0"), 0;
  For(k,1,n) {
    printf("x%d=%.2lf\n", k, a[k][n+1] / a[k][k]);
  }
  return 0;
}

/*
9 3       2         2 
0 3.66667 6.77778   2.77778 
0 0       -1.15152  2.75758 

9 0       2         -13.5526 
0 3.66667 0         19.0088 
0 0       -1.15152  2.75758
 */

by Max_hmt @ 2024-07-17 18:40:04

@Daniel_yao

#include <iostream>
#include <cstdio>
#include <cmath>
using namespace std;

int n ;
double a[110][110] ;

inline int read()
{
    int x=0,f=1; char c=getchar();
    while(c>'9'||c<'0') {if(c=='-') f=-1; c=getchar();}
    while(c>='0'&&c<='9') {x=x*10+c-'0'; c=getchar();}
    return f*x;
}

void gauss()
{
    for ( int i = 1 ; i <= n; ++i )
    {
        for ( int j = i + 1 ; j <= n ; ++j )
            if ( fabs(a[j][i]) > fabs(a[i][i]) )
                for ( int k = 1 ; k <= n + 1 ; ++k )
                    swap( a[i][k] , a[j][k] ) ;
        if ( fabs(a[i][i]) < 1e-8 ) continue ;
        for ( int j = 1 ; j <= n ; ++j )
        {
            if ( i == j ) continue ;
            if ( fabs(a[j][i]) < 1e-8 ) continue ;
            double r = a[i][i] / a[j][i] ;
            for ( int k = 1 ; k <= n + 1 ; ++k )
                a[j][k] = a[i][k] - a[j][k] * r ;
        }
    }
}

int main()
{
    n = read() ;
    for ( int i = 1 ; i <= n ; ++i )
        for ( int j = 1 ; j <= n + 1 ; ++j )
            scanf("%lf",&a[i][j]) ;
    gauss() ;
    int ok = 0 ;
    for ( int i = 1 ; i <= n ; ++i )
        if ( fabs(a[i][i]) < 1e-8 && fabs(a[i][n+1]) < 1e-8 )
        {
            ok = 1 ; break ;
        }
    if ( ok ) printf("No Solution\n") ;
    else for ( int i = 1 ; i <= n ; ++i ) printf("%.2lf\n",a[i][n+1] / a[i][i]) ; 
}

@Daniel_yao

by Daniel_yao @ 2024-07-17 19:05:52

@Max_hmt 不是这一道题qwq，而且我并不知道我的代码哪里错啦qwq

by Max_hmt @ 2024-07-17 19:17:13

@Daniel_yao 稍等，大佬，让蒟蒻康康