UVA 1563 - SETI (高斯消元+逆元)

UVA 1563 - SETI

#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;

const int N = 105;

int pow_mod(int x, int k, int mod) {
int ans = 1;
while (k) {
if (k&1) ans = ans * x % mod;
x = x * x % mod;
k >>= 1;
}
return ans;
}

int inv(int a, int n) {
return pow_mod(a, n - 2, n);
}

int t, p, n, A

;
char str
;

int hash(int c) {
if (c == '*') return 0;
return c - 'a' + 1;
}

void build() {
for (int i = 0; i < n; i++) {
A[i]
= hash(str[i]);
int tmp = 1;
for (int j = 0; j < n; j++) {
A[i][j] = tmp;
tmp = tmp * (i + 1) % p;
}
}
}

void gauss() {
for (int i = 0; i < n; i++) {
int r;
for (r = i; r < n; i++)
if (A[r][i]) break;
if (r == n) continue;
for (int j = i; j <= n; j++) swap(A[r][j], A[i][j]);
for (int j = 0; j < n; j++) {
if (i == j) continue;
if (A[j][i]) {
int tmp = A[j][i] * inv(A[i][i], p) % p;
for (int k = i; k <= n; k++) {
A[j][k] = (((A[j][k] - tmp * A[i][k]) % p) + p) % p;
}
}
}
}
for (int i = 0; i < n; i++)
printf("%d%c", A[i]
* inv(A[i][i], p) % p, i == n - 1 ? '\n' : ' ');
}

int main() {
scanf("%d", &t);
while (t--) {
scanf("%d%s", &p, str);
n = strlen(str);
build();
gauss();
}
return 0;
}