2023 蓝桥杯 C++ A组

发布时间 2023-04-10 15:59:23作者: Kidding_Ma

F

#include "bits/stdc++.h"

using namespace std;
using i64 = long long;

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    
    int n, m;
    cin >> n >> m;
    m *= 2;
    vector<int> a(n);
    for (int i = 0; i < n; i++) {
        cin >> a[i];
    }
    int N = n / 2;
    unordered_map<int, int> mp(1024);
    mp.max_load_factor(0.25);
    mp[0] = 0;
    function<void(int, int, int, i64)> dfs = [&](int j, int B, int res, i64 sum) {
        if (sum >= m || j == N) {
            if (sum <= m) {
                mp[sum] = res;
            }
            return;
        }
        if (B == 0) {
            sum += a[j];
            res++;
        } else if (B == 1) {
            sum += a[j] * 2;
        }
        for (int i = 0; i < 3; i++) {
            dfs(j + 1, i, res, sum);
        }
    };
    for (int i = 0; i < 3; i++) {
        dfs(0, i, 0, 0);
    }
    int ans = 1E9;
    function<void(int, int, int, i64)> dfs_again = [&](int j, int B, int res, i64 sum) {
        if (sum >= m || j == n) {
            if (sum <= m && mp.count(m - sum)) {
                ans = min(ans, mp[m - sum] + res);
            }
            return;
        }
        if (B == 0) {
            sum += a[j];
            res++;
        } else if (B == 1) {
            sum += a[j] * 2;
        }
        for (int i = 0; i < 3; i++) {
            dfs_again(j + 1, i, res, sum);
        }
    };
    for (int i = 0; i < 3; i++) {
        dfs_again(N, i, 0, 0);
    }
    cout << ans << '\n';

    return 0;
}