Code : Birthday Gift

#include <bits/stdc++.h>
using namespace std;

bool is_bit_set(int x, int i) { return ((1 << i) & x) != 0; }

bool is_rhs_submask(int mask, int sub) { return (mask | sub) == mask; }

int solve(vector<int> &a, int x) {
    x++;
    int n = a.size();

    int ans = -1;
    for (int bit = 0; bit <= 30; bit++) {
        if (!is_bit_set(x, bit)) {
            continue;
        }
        int goal = (x >> bit) - 1;
        int parts = 0, pref = 0, have = 0;
        for (int i = 0; i < n; i++) {
            pref ^= (a[i] >> bit);
            if (is_rhs_submask(goal, pref)) {
                have |= pref;
                pref = 0;
                parts++;
            }
        }
        // Code will work even without have == goal check. Why?
        if (is_rhs_submask(goal, pref) && have == goal) {
            ans = max(ans, parts);
        }
    }
    return ans;
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    int tt;
    cin >> tt;
    while (tt--) {
        int n, x;
        cin >> n >> x;
        vector<int> a(n);
        for (int i = 0; i < n; i++) {
            cin >> a[i];
        }
        int ans = solve(a, x);
        cout << ans << '\n';
    }
    return 0;
}

#include <bits/stdc++.h>
using namespace std;

bool is_bit_set(int x, int i) { return ((1 << i) & x) != 0; }

bool is_rhs_submask(int mask, int sub) { return (mask | sub) == mask; }

int solve(vector<int> &a, int x) {
    x++;
    int n = a.size();

    int ans = -1;
    for (int bit = 0; bit <= 30; bit++) {
        if (!is_bit_set(x, bit)) {
            continue;
        }
        int goal = (x >> bit) - 1;
        int parts = 0, pref = 0;
        for (int i = 0; i < n; i++) {
            pref ^= (a[i] >> bit);
            if (is_rhs_submask(goal, pref)) {
                parts++;
                pref = 0;
            }
        }
        if (is_rhs_submask(goal, pref)) {
            ans = max(ans, parts);
        }
    }
    return ans;
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    int tt;
    cin >> tt;
    while (tt--) {
        int n, x;
        cin >> n >> x;
        vector<int> a(n);
        for (int i = 0; i < n; i++) {
            cin >> a[i];
        }
        int ans = solve(a, x);
        cout << ans << '\n';
    }
    return 0;
}