UESTC - 878 温泉旅店 二维费用背包问题

#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <algorithm>
#include <assert.h>
#define IOS ios::sync_with_stdio(false)
using namespace std;
#define inf (0x3f3f3f3f)
typedef long long int LL;


#include <iostream>
#include <sstream>
#include <vector>
#include <set>
#include <map>
#include <queue>
#include <string>
#include <bitset>
const int maxn = 1e2 + 20;
int a[maxn], n;
int ans;
int dp[20][500 + 20][500 + 20];
void work() {
    ans = 0;
    for (int i = 1; i <= n; ++i) {
        scanf("%d", &a[i]);
    }
    dp[0][0][0] = true;
    for (int i = 1; i <= n; ++i) {
        for (int j = 0; j <= 500; ++j) {
            for (int k = 0; k <= 500; ++k) {
                if (dp[i - 1][j][k]) {
                    dp[i][j][k] += dp[i - 1][j][k];
                    dp[i][j ^ a[i]][k] += dp[i - 1][j][k];
                    dp[i][j][k ^ a[i]] += dp[i - 1][j][k];
//                    if (j <= k) ans++;
                }
            }
        }
    }
    for (int i = 0; i <= 500; ++i) {
        for (int j = 0; j <= 500; ++j) {
            if (dp[n][i][j] && i <= j) {
                ans += dp[n][i][j];
            }
        }
    }
    cout << ans << endl;
}

int main() {
#ifdef local
    freopen("data.txt", "r", stdin);
//    freopen("data.txt", "w", stdout);
#endif
    while (scanf("%d", &n) != EOF) work();
    return 0;
}