diff --git a/AcWing/2190/2190.cpp b/AcWing/2190/2190.cpp new file mode 100644 index 00000000..5580629a --- /dev/null +++ b/AcWing/2190/2190.cpp @@ -0,0 +1,133 @@ +#include +#include +#include +#include +#include + +using std::cin; +using std::cout; +const char endl = '\n'; + +const int N = 5e4 + 5, + M = 125003 + 5; + +int n, m, s, t, ss, tt; +int idx, head[N], ver[M << 2], edge[M << 2], next[M << 2]; +int f[N], cur[N], dist[N]; + +void add(int u, int v, int w) { + ver[idx] = v; + edge[idx] = w; + next[idx] = head[u]; + head[u] = idx++; +} + +bool bfs() { + memset(dist, 0x00, sizeof(dist)); + + std::queue q; + + q.push(s); + dist[s] = 1; + cur[s] = head[s]; + + while (!q.empty()) { + int u = q.front(); + q.pop(); + + for (int i = head[u]; ~i; i = next[i]) { + int v = ver[i], + w = edge[i]; + + if (!dist[v] && w) { + dist[v] = dist[u] + 1; + cur[v] = head[v]; + if (v == t) return true; + q.push(v); + } + } + } + + return false; +} + +int dinic(int u, int limit) { + if (u == t) return limit; + + int flow = 0; + for (int i = cur[u]; ~i && flow < limit; i = next[i]) { + cur[u] = i; + + int v = ver[i], + w = edge[i]; + + if (dist[v] == dist[u] + 1 && w) { + int k = dinic(v, std::min(w, limit - flow)); + + if (!k) dist[v] = 0; + edge[i] -= k; + edge[i ^ 1] += k; + flow += k; + } + } + + return flow; +} + +int main() { + std::ios::sync_with_stdio(false); + cin.tie(nullptr); + + memset(head, 0xff, sizeof(head)); + + cin >> n >> m >> ss >> tt; + + for (int i = 1, u, v, a, b; i <= m; i++) { + cin >> u >> v >> a >> b; + + add(u, v, b - a); + add(v, u, 0); + + f[u] -= a, f[v] += a; + } + + int sum = 0; + s = 0, t = n + 1; + + for (int i = 1; i <= n; i++) { + if (f[i] > 0) { + add(s, i, f[i]); + add(i, s, 0); + sum += f[i]; + } else if (f[i] < 0) { + add(i, t, -f[i]); + add(t, i, 0); + } + } + + add(tt, ss, std::numeric_limits::max()); + add(ss, tt, 0); + + int res = 0, flow; + while (bfs()) { + while (flow = dinic(s, std::numeric_limits::max())) res += flow; + } + + if (res == sum) { + int x = edge[idx - 1]; + edge[idx - 1] = edge[idx - 2] = 0; + + s = tt, t = ss; + + int res = 0, flow; + while (bfs()) { + while (flow = dinic(s, std::numeric_limits::max())) res += flow; + } + + cout << x - res << endl; + } else { + cout << "No Solution" << endl; + } + + return 0; +}