sgu275：To xor or not to xor(最大异或和)

来源：互联网发布：qq直播是什么软件编辑：程序博客网时间：2024/06/07 17:17

题目大意：
最大异或和。

分析：
就是高斯消元一发，正确性很显然，模板题都懒得讲了...

AC code：

#include <cstdio>#include <cmath>#include <cstdlib>#include <cstring>#include <cctype>#include <algorithm>#include <string>#include <sstream>#include <iostream>#include <map>#include <set>#include <list>#include <stack>#include <queue>#include <vector>#define get(s, x) (((s)>>(x))&1)#define pb push_back#define mp make_pairtypedef long long LL;typedef double DB;typedef long double LD;using namespace std;const int MAXN = 109;int n;LL a[MAXN];int main(){    #ifndef ONLINE_JUDGE    freopen("input.txt", "r", stdin);    freopen("output.txt", "w", stdout);    #endif    scanf("%d", &n);    for(int i = 1; i <= n; ++i)        cin >> a[i];    int st = 1;    for(int i = 63; i >= 0; --i)    {        bool flag = false;        for(int j = st; j <= n; ++j)            if(get(a[j], i))            {                swap(a[j], a[st]);                flag = true;break;            }        if(flag)        {            for(int j = 1; j <= n; ++j)                if(j != st && get(a[j], i))                    a[j] ^= a[st];            st++;        }    }    LL ans = 0;    for(int i = 1; i <= n; ++i)        ans ^= a[i];    cout << ans << endl;    #ifndef ONLINE_JUDGE    fclose(stdin);    fclose(stdout);    #endif    return 0;}

0 0