萌新求助高斯消元

WA #4 #8

不太会判断无解和无限解，求助qwq

#include<iostream>
#include<cstdio>
#include<cmath>
#include<bitset>
#include<cstdlib>
#include<cstring>
#include<algorithm>
#include<vector>
#include<queue>
#include<set>
#include<map>
using namespace std;
#define maxn 110
#define inf 0x7f7f7f7f
#define mod 1000000007
#define esp 1e-6 
#define re register
inline int read();
inline void wn(int x);
inline void wr(int x);
inline void wi(int x);
double a[maxn][maxn];
double ans[maxn];
int n;
signed main()
{
//  freopen("a.in","r",stdin);
//  freopen("a.out","w",stdout);
//  printf("%d M\n",((sizeof(z))>>20));
    cin>>n;
    for(re int i=1;i<=n;++i)    
        for(re int j=1;j<=n+1;++j)    
            scanf("%lf",&a[i][j]);
    for(re int i=1;i<=n;++i)
    {
        int m=i;
        for(re int j=i+1;j<=n;++j)
            if(fabs(a[j][i])>fabs(a[m][i]))     m=j;  
        if(fabs(a[m][i])<esp)   continue;
        if(m!=i)    swap(a[m],a[i]);
        double d=a[i][i];
        for(re int j=i;j<=n+1;++j)  
            a[i][j]/=d;
        for(re int j=i+1;j<=n;++j)
        {
            d=a[j][i];
            for(re int k=i;k<=n+1;++k)
            {
                a[j][k]-=a[i][k]*d;
            }
        }
    }
    //for(re int i=1;i<=n;++i,puts(""))
  //      for(re int j=1;j<=n+1;++j)
//            printf("%.2lf ",a[i][j]);
    bool p1=false,p2=false;
    for(re int i=1;i<=n;++i)    
        if(fabs(a[i][i])<esp&&fabs(a[i][n+1])>esp)  
        {
            p1=true;
            break;
        }
    if(p1)
    {
        puts("-1");
        return 0;
    }
    for(re int i=1;i<=n;++i)    
        if(fabs(a[i][i])<esp&&fabs(a[i][n+1])<esp)  
        {
            p2=true;
            break;
        }
    if(p2)
    {
        wr(0);
        return 0;
    }
    ans[n]=a[n][n+1];
    for(re int i=n-1;i>=1;--i)
    {
        ans[i]=a[i][n+1];
        for(re int j=i+1;j<=n;++j)
            ans[i]-=a[i][j]*ans[j];
    }
    for(re int i=1;i<=n;++i,puts(""))
        (fabs(ans[i])<esp)?printf("x%d=%.2lf",i,0.00):printf("x%d=%.2lf",i,ans[i]);
    return 0;
}
//==========================================================
inline int read()
{
    int f=1,x=0;
    char ch=getchar();
    while(ch<'0'||ch>'9')
    {
        if(ch=='-') f=-1;
        ch=getchar();
    }
    while(ch>='0'&&ch<='9')
    {
        x=(x<<3)+(x<<1)+ch-'0';
        ch=getchar();
    }
    return x*f;
}
inline void wn(int x)
{
    if(x<0)
    {
        putchar('-');
        wn(-x);
        return ;
    }
    if(x>=10)   wn(x/10);
    putchar('0'+x%10);
}
inline void wr(int x)
{
    wn(x);
    putchar('\n');
}
inline void wi(int x)
{
    wn(x);
    putchar(' ');
}