HDU3915 Game 高斯消元

题目链接

HDU3915 Game 高斯消元

题解

求异或方程组自由元的子集个数

高斯消元求秩,内存溢出好神

代码

#include<bitset>
#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std ;
inline int read() {
	int x = 0,f = 1;
	char c = getchar();
	while(c < '0' ||c > '9'){if(c == '-') f = -1;c = getchar();}
	while(c <= '9' && c >= '0') x = x * 10 + c - '0',c = getchar();
	return x * f;
}
bitset<105>a[32];
int n;
void gauss(int equ ,int var) {
	int r , c , t ;
	for(r = c = 1;r <= equ && c <= var;++ r ,++ c) {
		t = r;
		for(;t < equ;++ t) if(a[t][c]) break ;
		if(t == equ) {
			-- r ;continue ;
		} else swap(a[t] , a[r]);
		for(int i = r + 1;i <= equ;++ i) if (a[i][c]) a[i] ^= a[r];
	}
	int n = var - r , ans = 1;
	for(int i = 1;i <= n;++ i) {
		ans <<= 1 ;ans %= 1000007;
	}
	printf("%d\n",ans);
}
int main () {
	int T = read();
	while(T --) {
		for(int i = 1;i <= 31; ++ i) a[i] = 0;
		n = read();
		for(int x,i = 1;i <= n;++ i) {
			x = read();
			for(int j = 1;j <= 31;++ j) a[j][i] = ((x >> j) & 1);//,printf("%d\n",n);
		}
		gauss(31,n);
	}
	return 0 ;
}