HDU - 5119 Happy Matt Friends（DP）

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题目大意：给你N个数，问有多少个子集，满足子集内所有数的xor和大于等于M

解题思路：用dp[i][j]表示前i个数，xor和为j的情况有多少种
则dp[i][j] = dp[i - 1][j]，表示第i个数不选
dp[i][j ^ val[i]] += dp[i][j]，表示选了第i个数

#include <cstdio>#include <cstring>#include <algorithm>using namespace std;typedef long long LL;const int N = (1 << 20) + 10;LL dp[41][N];int n, m, cnt, cas = 1;int val[41];void init() {    scanf("%d%d", &n, &m);    int Max = 0;    for (int i = 0; i < n; i++) {        scanf("%d", &val[i]);        Max = max(Max, val[i]);    }    cnt = 0;    while (Max) {        cnt++;        Max /= 2;    }}void solve() {    int All = 1 << cnt;    for (int i = 0; i < n; i++)        for (int j = 0; j < All; j++)            dp[i][j] = 0;    dp[0][0] = dp[0][val[0]] = 1;    for (int i = 1; i < n; i++)        for (int j = 0; j < All; j++) {            dp[i][j] += dp[i - 1][j];            dp[i][j ^ val[i]] += dp[i - 1][j];        }    LL ans = 0;    for (int i = m; i < All; i++)        ans += dp[n - 1][i];    printf("Case #%d: %lld\n", cas++, ans);}int main() {    int test;    scanf("%d", &test);    while (test--) {        init();        solve();    }    return 0;}

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