hdu 3949 Xor (高斯消元解决xor问题）

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题目：http://acm.hdu.edu.cn/showproblem.php?pid=3949

#include<iostream>#include<cstdio>#include<cstring>#include<map>#include<algorithm>#include<cmath>#include<queue>#include<stack>using namespace std;#define M 10010#define inf 1LL<<60#define ll long long#define eps 1e-7#define bas 9#define mod 1000000000LLll a[M];ll bit[61];int n;void gauss(){    int row = 0, col = 60, k;    while( col >= 0 && row < n ){        k = row;        while( k < n && (a[k]&bit[col]) == 0 ) ++k;        if( k == n ){            --col;        }        else{            swap( a[row], a[k] );            for( int i = 0; i < n; ++i ) if( i-row ){                if( a[i]&bit[col] ) a[i] ^= a[row];            }            --col, ++row;        }    }    sort( a, a+n );    n = unique( a, a+n ) - a;}ll cal( int x ){    int i = 0;    if( a[0] == 0 ){        if( x == 1 ) return 0;        ++i;        --x;    }    ll ans = 0;    while( x && i < n ){        if(x&1) ans ^= a[i];        x >>= 1;        ++i;    }    if( x ) return -1;    return ans;}int main(){    //freopen( "input.txt", "r", stdin );    //freopen( "output.txt", "w", stdout );    bit[0] = 1;    for( int i = 1; i < 61; ++i ) bit[i] = bit[i-1]<<1;    int T, q, t = 0, x;    scanf( "%d", &T );    while( T-- ){        scanf( "%d", &n );        for( int i = 0; i < n; ++i ) scanf( "%I64d", a+i );        gauss();        printf( "Case #%d:\n", ++t );        scanf( "%d", &q );        while( q-- ){            scanf( "%d", &x );            cout<<cal(x)<<endl;        }    }}