poj 2065 还是gauss消元

#include <cstdio>
#include <cstring>
#include <iostream>
#include <queue>
#include <vector>
#include <stack>
#include <cmath>

using namespace std;

const int M = 10005;
const int maxn = 1000000;
typedef long long LL;

int a[75][75];
int x[75];
char s[75];
int equ,var,p;

int gcd(int a,int b)
{
    if(b == 0) return a;
    else return gcd(b,a%b);

}

int lcm(int a,int b)
{
    return (a/gcd(a,b))*b;
}

void gauss()
{
    int k,col = 0;
    for(k=0;k<equ&&col<var;k++,col++){
        int mx_r = k; //找最大的行
        for(int i=k+1;i<equ;i++){
            if(abs(a[i][col])>abs(a[mx_r][col])) mx_r = i;
        }
        if(mx_r != k){
            for(int i=k;i<=var;i++) swap(a[k][i],a[mx_r][i]);
        }
        if(a[k][col] == 0){ k--;continue;}
        for(int i=k+1;i<equ;i++){
            if(a[i][col] != 0){
                int lc = lcm(abs(a[i][col]),abs(a[k][col]));
                int ta = lc/abs(a[i][col]);
                int tb = lc/abs(a[k][col]);
                if(a[i][col]*a[k][col]<0) tb = -tb;
                for(int j=col;j<=var;j++){
                   a[i][j] = ((a[i][j]*ta-a[k][j]*tb)%p+p)%p;
                }
            }
        }
    }
    int temp;
    for(int i=var-1;i>=0;i--){
         temp = a[i][var];
        for(int j=i+1;j<var;j++){
            if(a[i][j] != 0) temp -= a[i][j]*x[j];
            temp = (temp%p+p)%p;
        }
        while(temp % a[i][i]!=0) temp+=p;
        x[i] = (temp/a[i][i])%p;
    }
    for(int i=0;i<var-1;i++){
        printf("%d ",x[i]);
    }
    printf("%d
",x[var-1]);
}

int pow_mod(int a,int n,int MOD)
{
    int ret=1;
    int temp=a%MOD;
    while(n)
    {
        if(n&1){ret*=temp;ret%=MOD;}
        temp*=temp;
        temp%=MOD;
        n>>=1;
    }
    return ret;
}

void init()
{

    memset(x,0,sizeof(x));
    memset(a,0,sizeof(a));
    memset(s,0,sizeof(s));
    scanf("%d",&p);
    scanf("%s",s);
    int len = strlen(s);
    equ = var = len;
    for(int i=0;i<len;i++){
        if(s[i] == '*') a[i][var] = 0;
        else a[i][var] = s[i]-'a'+1;
        for(int j=0;j<len;j++){
            a[i][j] = pow_mod(i+1,j,p);
        }
    }
}


int main()
{
    int t;
    scanf("%d",&t);
    while(t--){
        init();
        gauss();
    }

    return 0;
}