#include <stdio.h>
#include <math.h>
#include <stdlib.h>
#include <string.h>
#define INP_FILE in_file
#define OUT_FILE out_file
typedef struct queue_cell {
int value;
struct queue_cell *next;
} QCell, *TQCell;
typedef struct squeue {
TQCell head;
TQCell tail;
} Queue, *TQueue;
void enqueue(TQueue queue, int val)
{
TQCell cell = (TQCell) malloc(sizeof(*cell));
cell->value = val;
cell->next = NULL;
if (queue->head == NULL) {
queue->head = cell;
queue->tail = cell;
return;
}
queue->tail->next = cell;
queue->tail = cell;
return;
}
int dequeue(TQueue queue)
{
int value = queue->head->value;
if (queue->head == queue->tail) {
free(queue->head);
queue->head = queue->tail = NULL;
return value;
}
TQCell aux = queue->head;
queue->head = queue->head->next;
free(aux);
return value;
}
void destroy_queue(TQueue queue)
{
while (queue->head != NULL) {
dequeue(queue);
}
free(queue);
return;
}
typedef struct dgraph_edge {
int id;
double cost;
double flow;
struct dgraph_edge *next;
} DGEdge, *TDGEdge;
typedef struct dgraph {
int V, E;
TDGEdge *out_edges;
} DGraph, *TDGraph;
void make_and_add_edges(TDGraph graph, int v1, int v2, double cost)
{
TDGEdge edge_out = (TDGEdge) calloc(1, sizeof(*edge_out));
edge_out->id = v2;
edge_out->cost = cost;
edge_out->flow = 0;
edge_out->next = graph->out_edges[v1];
graph->out_edges[v1] = edge_out;
return;
}
void make_res_graph_edges(TDGraph graph, TDGraph res_graph)
{
for (int i = 0; i < graph->V; i++) {
TDGEdge iter = graph->out_edges[i];
while (iter != NULL) {
make_and_add_edges(res_graph, i, iter->id, iter->cost - iter->flow);
make_and_add_edges(res_graph, iter->id, i, iter->flow);
iter = iter->next;
}
}
return;
}
int make_level_graph_edges(TDGraph res_graph, TDGraph level_graph)
{
int V = res_graph->V;
int *levels = (int *) calloc(V, sizeof(int));
TQueue queue = (TQueue) malloc(sizeof(*queue));
queue->head = queue->tail = NULL;
enqueue(queue, 0);
int current_vertex;
while (queue->head != NULL) {
current_vertex = dequeue(queue);
TDGEdge iter = res_graph->out_edges[current_vertex];
while (iter != NULL) {
if ((levels[iter->id] != 0 && levels[iter->id] <= levels[current_vertex]) ||
iter->cost <= 0 || iter->id == 0) {
iter = iter->next;
continue;
}
make_and_add_edges(level_graph, current_vertex, iter->id, iter->cost);
levels[iter->id] = levels[current_vertex] + 1;
enqueue(queue, iter->id);
iter = iter->next;
}
}
if (levels[V - 1] == 0) {
return 0;
}
return 1;
}
void update_flow(TDGraph graph, int v1, int v2, double flow)
{
TDGEdge iter = graph->out_edges[v1];
while (iter != NULL) {
if (iter->id == v2) {
iter->flow += flow;
return;
}
iter = iter->next;
}
iter = graph->out_edges[v2];
while (iter != NULL) {
if (iter->id == v1) {
iter->flow -= flow;
return;
}
iter = iter->next;
}
return;
}
void update_cost_level_graph(TDGraph graph, int v1, int v2, double cost)
{
TDGEdge iter = graph->out_edges[v1];
while (iter != NULL) {
if (iter->id == v2) {
iter->cost -= cost;
return;
}
iter = iter->next;
}
return;
}
void update_res(TDGraph res_graph, int v1, int v2, double flow)
{
TDGEdge iter = res_graph->out_edges[v1];
while (iter != NULL) {
if (iter->id == v2) {
iter->cost -= flow;
break;
}
iter = iter->next;
}
iter = res_graph->out_edges[v2];
while (iter != NULL) {
if (iter->id == v1) {
iter->cost += flow;
return;
}
iter = iter->next;
}
}
void dfs_once_level_graph(int *parents, double *costs_to_parents, TDGraph level_graph, int vertex)
{
if (parents[level_graph->V - 1] != -1) {
return;
}
TDGEdge iter = level_graph->out_edges[vertex];
while (iter != NULL) {
if (iter->cost <= 0) {
iter = iter->next;
continue;
}
parents[iter->id] = vertex;
costs_to_parents[iter->id] = iter->cost;
dfs_once_level_graph(parents, costs_to_parents, level_graph, iter->id);
iter = iter->next;
}
return;
}
void dfs_until_bf_and_modify_graphs(TDGraph graph, TDGraph res_graph, TDGraph level_graph)
{
int V = level_graph->V;
int *parents = (int *) calloc(V, sizeof(parents));
double *costs_to_parents = (double *) malloc(V * sizeof(double));
parents[0] = -1;
parents[V - 1] = -1;
dfs_once_level_graph(parents, costs_to_parents, level_graph, 0);
while (parents[V - 1] != -1) {
double critical_cost = (int)0x7fffffff;
int last = V - 1;
while (last != 0) {
if (costs_to_parents[last] < critical_cost) {
critical_cost = costs_to_parents[last];
}
last = parents[last];
}
int current_vertex = V - 1;
int current_parent = parents[current_vertex];
while (parents[current_vertex] != -1) {
update_flow(graph, current_parent, current_vertex, critical_cost);
update_res(res_graph, current_parent, current_vertex, critical_cost);
update_cost_level_graph(level_graph, current_parent, current_vertex, critical_cost);
current_vertex = current_parent;
current_parent = parents[current_vertex];
}
for (int i = 1; i < V; i++) {
parents[i] = 0;
}
parents[V - 1] = -1;
dfs_once_level_graph(parents, costs_to_parents, level_graph, 0);
}
return;
}
void free_graph(TDGraph graph)
{
int V = graph->V;
for (int i = 0; i < V; i++) {
TDGEdge iter = graph->out_edges[i];
TDGEdge aux;
while (iter != NULL) {
aux = iter->next;
free(iter);
iter = aux;
}
}
free(graph->out_edges);
free(graph);
return;
}
void free_edges(TDGraph level_graph)
{
int V = level_graph->V;
for (int i = 0; i < V; i++) {
TDGEdge iter = level_graph->out_edges[i];
TDGEdge aux;
while (iter != NULL) {
aux = iter->next;
free(iter);
iter = aux;
}
}
for (int i = 0; i < V; i++) {
level_graph->out_edges[i] = NULL;
}
return;
}
double dinic_max_flow(TDGraph graph)
{
TDGraph res_graph = (TDGraph) malloc(sizeof(*res_graph));
res_graph->V = graph->V;
res_graph->E = 2 * graph->E;
res_graph->out_edges = (TDGEdge *) calloc(res_graph->V, sizeof(TDGEdge));
make_res_graph_edges(graph, res_graph);
TDGraph level_graph = (TDGraph) malloc(sizeof(*level_graph));
level_graph->V = graph->V;
level_graph->out_edges = (TDGEdge *) calloc(res_graph->V, sizeof(TDGEdge));
level_graph->E = 0;
int there_is_path = make_level_graph_edges(res_graph, level_graph);
while (there_is_path == 1) {
dfs_until_bf_and_modify_graphs(graph, res_graph, level_graph);
free_edges(level_graph);
there_is_path = make_level_graph_edges(res_graph, level_graph);
}
double flow = 0;
TDGEdge iter = graph->out_edges[0];
while (iter != NULL) {
flow += iter->flow;
iter = iter->next;
}
free_graph(res_graph);
return flow;
}
int main( int argc, const char* args[] )
{
TDGraph graph = (TDGraph) malloc(sizeof(*graph));
FILE *in_file = fopen("maxflow.in", "r");
FILE *out_file = fopen("maxflow.out", "w");
fscanf(INP_FILE, "%d%d", &graph->V, &graph->E);
graph->out_edges = (TDGEdge *) calloc(graph->V, sizeof(TDGEdge));
int v1, v2;
double cost;
for (int i = 0; i < graph->E; i++) {
fscanf(INP_FILE, "%d%d%lf", &v1, &v2, &cost);
v1--;
v2--;
if (v2 == 0 || v1 == graph->V - 1) {
printf("Vertex giving to source or taking from sink.\n");
return 1;
}
make_and_add_edges(graph, v1, v2, cost);
}
double max_flow = dinic_max_flow(graph);
fprintf(OUT_FILE, "%d\n", (int)max_flow);
free_graph(graph);
return 0;
}