| # | Time | Username | Problem | Language | Result | Execution time | Memory |
|---|---|---|---|---|---|---|---|
| 1296801 | SzymonKrzywda | Svjetlo (COCI20_svjetlo) | C++20 | 0 ms | 0 KiB |
#include <iostream>
#include <vector>
using namespace std;
const int MAXN = 5e5 + 7;
vector<int> graf[MAXN];
int dp[MAXN][2][2]; //zmiana parent, koncze w v
bool color[MAXN];
void dfs(int v, int p) {
if (v != p && graf[v].size() == 1) {
if (color[v]) {
dp[v][0][0] = 0;
dp[v][0][1] = 0;
dp[v][1][1] = 0;
return;
}
dp[v][0][0] = 1;
dp[v][0][1] = 1;
dp[v][1][1] = 3;
return;
}
int xorr = (graf[v].size()) % 2, optsuma = graf[v].size() + (v == p);
if (v == p) xorr ^= 1;
xorr ^= color[v];
for (int s : graf[v]) {
if (s != p) {
dfs(s, v);
if (dp[s][0][1] > dp[s][1][1]) xorr ^= 1;
optsuma += min(dp[s][0][1], dp[s][1][1]);
}
}
dp[v][0][0] = 1e9;
dp[v][0][1] = 1e9;
dp[v][1][1] = 1e9;
for (int s : graf[v]) {
if (s == p) continue;
int oh = dp[s][0][1] > dp[s][1][1];
int optsuma2 = optsuma - min(dp[s][0][1], dp[s][1][1]);
//cout << "O: " << v << ' ' << ' ' << min(dp[s][0][1], dp[s][1][1]) << ' ' << optsuma << ' ' << optsuma2 << '\n';
dp[v][0][0] = min(dp[v][0][0], optsuma2 + dp[s][0][0] + (xorr ^ oh) * (int)1e7 - 1);
}
if (!xorr) dp[v][1][1] = optsuma + 3;
else dp[v][0][1] = optsuma;
dp[v][0][0] = min(dp[v][0][0], dp[v][0][1]);
//cout << v << ": " << dp[v][0][0] << ' ' << dp[v][0][1] << ' ' << dp[v][1][1] << ' ' << optsuma << ' ' << xorr << '\n';
}
int main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
int n, a, b;
cin >> n;
char c;
for (int i = 1; i <= n; i++) {
cin >> c;
color[i] = c - '0';
}
for (int i = 0; i < n - 1; i++) {
cin >> a >> b;
graf[a].push_back(b);
graf[b].push_back(a);
}
int ans = 1e9;
for (int i = 1; i <= n; i++) {
dfs(i, i);
// cout << dp[i][0][0] << ' ' << dp[i][0][1] << ' ' << dp[i][1][1] << '\n';
ans = min({ans, dp[i][0][0], dp[i][0][1], dp[i][1][1]});
}
cout << ans << '\n';
return 0;
}
