[Network stream Topic 4] least vertex weight coverage set

Example of the maximum stream BFS print + + Code \ n

Ahead

11.1.2018

Example

Poj 2125

Select some vertices to overwrite all edges.
It is still the minimum cut and cut point. For the two points of each edge, the source point is connected to each point to delete the weight of all edges starting from this point, that is, W -, similarly, W + center links are divided into graph edge relationships for each point to the sink point.
Then the maximum stream is enough.
A deep search is required for the solution. If the node connected to the source node cannot be accessed, it must be cut off, the access to the vertex must be cut off.

Code

# Include <iostream> # include <cstdlib> # include <cstdio> # include <cstring> # include <queue> using namespace STD; const int S = 1000, t = 1001; const int n = 40000, INF = 0x3f3f3f; int n, m; int to [n <1], NXT [n <1], last [N], W [n <1], Len = 1; inline void ins (int x, int y, int c) {to [++ Len] = Y, NXT [Len] = last [X], W [Len] = C, last [x] = Len;} int H [N]; bool vis [N]; bool BFS () {memset (H, 0, sizeof (h); queue <int> q; vis [s] = 1; q. push (S); H [s] = 1; while (! Q. empty () {int x = Q. front (); q. pop (); vis [x] = 0; For (int K = last [X]; k = NXT [k]) {int y = to [k]; if (W [k] &! H [y]) {H [y] = H [x] + 1; if (! Vis [y]) {vis [y] = 1; q. Push (y) ;}}} return H [T]! = 0;} int DFS (int x, int flow) {If (x = T) return flow; int res = flow; For (int K = last [x]; k; k = NXT [k]) {int y = to [k]; If (W [k] & H [y] = H [x] + 1) {int T = DFS (Y, min (W [K], Res); W [k]-= T; W [k ^ 1] + = T; res-= T; If (RES = 0) break;} If (RES = flow) H [x] = 0; Return Flow-res ;} inline int dinic () {int maxflow = 0; while (BFS () {int TMP = DFS (S, INF); While (TMP) {maxflow + = TMP; TMP = DFS (S, INF) ;}return maxflow;} Bo Ol OK [N]; void DFS (int x) {OK [x] = 1; for (int K = last [X]; k = NXT [k]) {int y = to [k]; If (! OK [y] & W [k]) DFS (y) ;}} int main () {int x, y, z; scanf ("% d ", & N, & M); For (INT I = 1; I <= N; ++ I) {scanf ("% d", & Z ); INS (I + N, T, Z), INS (t, I + N, 0) ;}for (INT I = 1; I <= N; ++ I) {scanf ("% d", & Z); ins (S, I, Z), INS (I, S, 0) ;}for (INT I = 1; I <= m; ++ I) {scanf ("% d", & X, & Y); ins (X, Y + N, INF ), INS (Y + n, x, 0);} printf ("% d \ n", dinic (); int res = 0; DFS (s ); for (INT I = 1; I <= N; I ++) {If (! OK [I]) RES ++; If (OK [I + N]) RES ++;} printf ("% d \ n", Res ); for (INT I = 1; I <= N; I ++) {If (! OK [I]) printf ("% d-\ n", I); If (OK [I + N]) printf ("% d + \ n ", i);} return 0 ;}

network stream Topic 4: minimum point weight coverage set