Submission #755749

#	Time	Username	Problem	Language	Result	Execution time	Memory
755749		gnu	The Xana coup (BOI21_xanadu)	C++14	0 / 100	127 ms	34720 KiB

xanadu

#include <iostream>
#include <vector>
using namespace std;
using ll = long long;
vector<vector<vector<ll>>> dp;
vector<int> state;
void dfs(int u, int p, vector<vector<int>>& gp)
{
        ll sum1 = 0, cnt1 = 0, mn1 = 1e18, sum2 = 0, cnt2 = 0, mn2 = 1e18;
        for (int v : gp[u]) {
                if (v == p) continue;

                dfs(v, u, gp);
                if (dp[v][1][0] < dp[v][0][0]) {
                        sum1 += dp[v][1][0];
                        ++cnt1;
                }
                else {
                        sum1 += dp[v][0][0];
                }
                mn1 = min(mn1, abs(dp[v][1][0] - dp[v][0][0]));
                if (dp[v][1][1] < dp[v][0][1]) {
                        sum2 += dp[v][1][1];
                        ++cnt2;
                }
                else {
                        sum2 += dp[v][0][1];
                }
                mn2 = min(mn2, abs(dp[v][1][1] - dp[v][0][1]));

        }
        if (gp[u].size() == 1 && u != 0) {
                if (state[u]) {
                        dp[u][1][0] = 1;
                        dp[u][0][0] = 1e18;
                        dp[u][1][1] = 1e18;
                        dp[u][0][1] = 0;
                }
                else {
                        dp[u][1][0] = 1e18;
                        dp[u][0][0] = 0;
                        dp[u][1][1] = 1;
                        dp[u][0][1] = 1e18;
                }
                return;
        }
        if ((cnt1 & 1) && state[u] || !(cnt1 & 1) && !state[u]) {
                dp[u][0][0] = sum1;
        }
        else {
                dp[u][0][0] = sum1 + mn1;
        }
        state[u] = !state[u];
        if ((cnt2 & 1) && state[u] || !(cnt2 & 1) && !state[u]) {
                dp[u][1][0] = sum2+1;
        }
        else {
                dp[u][1][0] = sum2 + mn2+1;
        }


        if ((cnt1 & 1) && state[u] || !(cnt1 & 1) && !state[u]) {
                dp[u][0][1] = sum1;
        }
        else {
                dp[u][0][1] = sum1 + mn1;
        }

        state[u] = !state[u];
        if ((cnt2 & 1) && state[u] || !(cnt2 & 1) && !state[u]) {
                dp[u][1][1] = sum2+1;
        }
        else {
                dp[u][1][1] = sum2 + mn2+1;
        }


}

void solve()
{
        int n; cin >> n;
        vector<vector<int>> gp(n);
        state = vector<int>(n);
        dp = vector<vector<vector<ll>>>(n, vector<vector<ll>>(2, vector<ll>(2)));
        for (int i = 0; i < n - 1; ++i) {
                int u, v; cin >> u >> v; --u; --v;
                gp[u].push_back(v);
                gp[v].push_back(u);
        }
        for (int& x : state) {cin >> x;x=!x;}
        dfs(0, -1, gp);
        if (min(dp[0][0][0], dp[0][1][0]) <= n) {
                cout << min(dp[0][0][0], dp[0][1][0]) << '\n';
        }
        else {
                cout <<"IMPOSSIBLE";
        }


}
int main()
{
        //int t; cin >> t; while (t--)
                solve();
}

Compilation message (stderr)

xanadu.cpp: In function 'void dfs(int, int, std::vector<std::vector<int> >&)':
xanadu.cpp:47:24: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
   47 |         if ((cnt1 & 1) && state[u] || !(cnt1 & 1) && !state[u]) {
xanadu.cpp:54:24: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
   54 |         if ((cnt2 & 1) && state[u] || !(cnt2 & 1) && !state[u]) {
xanadu.cpp:62:24: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
   62 |         if ((cnt1 & 1) && state[u] || !(cnt1 & 1) && !state[u]) {
xanadu.cpp:70:24: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
   70 |         if ((cnt2 & 1) && state[u] || !(cnt2 & 1) && !state[u]) {

• Subtask 1: 0 / 5
• Subtask 2: 0 / 15
• Subtask 3: 0 / 10
• Subtask 4: 0 / 40
• Subtask 5: 0 / 30