174 lines
3.6 KiB
C++
174 lines
3.6 KiB
C++
/* Problem URL: https://cses.fi/problemset/task/1694 */
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#include <bits/stdc++.h>
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using namespace std;
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#define V vector
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#define rmin(a, b) a = min(a, b)
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#define rmax(a, b) a = max(a, b)
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#define rep(i, lim) for (size_t i = 0; i < (lim); i++)
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#define nrep(i, s, lim) for (size_t i = s; i < (lim); i++)
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#define repv(i, v) for (auto &i : (v))
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#define fillv(v) for (auto &itr_ : (v)) { cin >> itr_; }
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#define sortv(v) sort(v.begin(), v.end())
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#define all(v) (v).begin(), (v).end()
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using vi = vector<int>;
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using vvi = vector<vi>;
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using vvvi = vector<vvi>;
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using vvvvi = vector<vvvi>;
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using ll = long long;
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using vl = vector<ll>;
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using vvl = vector<vl>;
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using vvvl = vector<vvl>;
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using vvvvl = vector<vvvl>;
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template<class v>
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auto operator<<(ostream &os, const vector<v> &vec)->ostream& {
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os << vec[0];
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for (size_t i = 1; i < vec.size(); i++) {
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os << ' ' << vec[i];
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}
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os << '\n';
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return os;
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}
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template<class v>
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auto operator>>(istream &is, vector<v> &vec)->istream& {
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for (auto &i : vec) {
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is >> i;
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}
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return is;
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}
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template<class v>
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auto operator<<(ostream &os, const vector<vector<v>> &vec)->ostream& {
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for (auto &i : vec) {
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os << i[0];
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for (size_t j = 1; j < i.size(); j++) {
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os << ' ' << i[j];
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}
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os << '\n';
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}
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return os;
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}
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template<class v>
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auto operator>>(istream &is, vector<vector<v>> &vec)->istream& {
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for (auto &i : vec) {
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for (auto &j : i) {
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is >> j;
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}
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}
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return is;
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}
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int main()
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{
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ios::sync_with_stdio(false);
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cin.tie(nullptr);
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int n, m;
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cin >> n >> m;
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vvi graph(n);
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V<tuple<int, ll, ll>> edges;
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while (m--) {
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ll a, b, c;
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cin >> a >> b >> c;
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a--, b--;
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graph[a].push_back(edges.size());
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edges.emplace_back(b, c, 0);
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graph[b].push_back(edges.size());
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edges.emplace_back(a, 0, 0);
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}
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int inf = INT32_MAX >> 1;
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auto flux = [&](){
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vi level(n);
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auto bfs = [&](){
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queue<int> q;
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level[0] = 0;
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q.push(0);
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while (!q.empty()) {
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int i = q.front();
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q.pop();
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for (auto id : graph[i]) {
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auto [j, c, u] = edges[id];
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if (level[i] + 1 < level[j] && c != u) {
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level[j] = level[i] + 1;
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q.push(j);
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}
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}
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}
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return level[n - 1] != inf;
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};
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V<bool> vis(n);
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function<ll(int, ll)> dfs = [&](int i, ll flux){
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if (flux == 0) {
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return 0LL;
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}
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if (i == n - 1) {
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return flux;
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}
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for (auto id : graph[i]) {
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auto &[j, c, u] = edges[id];
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if (level[i] >= level[j] || vis[j]) {
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continue;
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}
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ll ans = dfs(j, min(flux, c - u));
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if (ans == 0) {
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continue;
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}
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auto &[_, __, ud] = edges[id ^ 1];
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u += ans;
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ud -= ans;
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return ans;
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}
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vis[i] = true;
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return 0LL;
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};
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ll ans = 0;
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while (true) {
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fill(all(level), inf);
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if (!bfs()) {
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break;
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}
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fill(all(vis), false);
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ll pushed = 0;
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while ((pushed = dfs(0, inf))) {
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ans += pushed;
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}
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}
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return ans;
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};
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cout << flux() << '\n';
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}
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