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Ford_fulkerson.c
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Ford_fulkerson.c
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#include<stdio.h>
#include<stdlib.h>
#define WHITE 0
#define GRAY 1
#define BLACK 2
#define MAX_NODES 1000
#define o 1000000
int n;
int e;
int capacity[MAX_NODES][MAX_NODES];
int flow[MAX_NODES][MAX_NODES];
int colour[MAX_NODES];
int pred[MAX_NODES];
int min(int x,int y){
return x<y ? x:y;
}
int head;
int tail;
int q[MAX_NODES+2];
void enqueue(int x){
q[tail] = x;
tail++;
colour[x] = GRAY;
}
int dequeue(){
int x = q[head];
head++;
colour[x] = BLACK;
return x;
}
int bfs(int start,int target){
int u,v;
for(u=0;u<n;u++){
colour[u] = WHITE;
}
head = tail = 0;
enqueue(start);
pred[start] = -1;
while(head != tail){
u = dequeue();
for(v=0;v<n;v++){
if(colour[v] == WHITE && capacity[u][v] - flow[u][v] > 0){
enqueue(v);
pred[v] = u;
}
}
}
return colour[target]==BLACK;
}
int max_flow(int source, int sink){
int i,j,u;
int max_flow = 0;
for(i=0;i<n;i++){
for(j=0;j<n;j++){
flow[i][j] = 0;
}
}
while(bfs(source,sink)){
int increment = o;
for(u=n-1; pred[u]>=0; u=pred[u]){
increment = min(increment, capacity[pred[u]][u] - flow[pred[u]][u]);
}
for(u=n-1;pred[u]>=0;u=pred[u]){
flow[pred[u]][u] = flow[pred[u]][u] + increment;
flow[u][pred[u]] = flow[u][pred[u]] - increment;
}
max_flow = max_flow + increment;
}
return max_flow;
}
int main(){
int a,b,c;
scanf("%d %d",&n,&e);
for(int i=0;i<n;i++){
for(int j=0;j<n;j++){
capacity[i][j] = 0;
}
}
for(int i=0;i<e;i++){
scanf("%d %d %d",&a,&b,&c);
capacity[a][b] = c;
}
printf("\nMax flow = %d",max_flow(0,3));
return 0;
}