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/*******************************************************/
/* 2nd Takehome Assignment */
/* Maximum matching marriage couples using */
/* Ford Fulkerson Algorithm */
/*Instructions : */
/* Data should be input to the program using text */
/* file (EX: test.txt) */
/* INPUT FORMAT: */
/* 10 10 */
/* 1 6 */
/* 1 7 */
/* 2 7 */
/* 3 6 */
/* 3 8 */
/* 3 10 */
/* 4 7 */
/* 4 10 */
/* 5 7 */
/* 5 9 */
/* first two integers (n and e) */
/* n: number of nodes in the graph */
/* e: number of incedent edges */
/* next integer(u,v) */
/* g[u][v]: adjecent verteces */
/*******************************************************/
#include <stdio.h>
#include <stdlib.h>
// Basic Definitions
#define WHITE 0 //nodes status
#define GRAY 1
#define BLACK 2
#define MAX_NODES 1000 //maximum allowed nodes
#define INFINITY 1000000000
// variable Declarations
int n; // number of nodes
int e; // number of edges
int capacity[MAX_NODES][MAX_NODES]; // capacity matrix
int flow[MAX_NODES][MAX_NODES]; // flow matrix
int color[MAX_NODES]; // store node status
int parent[MAX_NODES]; // array to store augmenting path
int min (int x, int y) {
return x<y ? x : y; // returns minimum of x and y
}
// A Queue for Breadth-First Search
int head,tail;
int q[MAX_NODES+2];
void enqueue (int x) { //add to queue
q[tail] = x;
tail++;
color[x] = GRAY;
}
int dequeue () { //remove from queue
int x = q[head];
head++;
color[x] = BLACK;
return x;
}
// Breadth-First Search for an augmenting path
int bfs (int start, int target) {
int u,v;
for (u=0; u<n+2; u++) { //initialize node status
color[u] = WHITE;
}
head = tail = 0;
enqueue(start);
parent[start] = -1;
while (head!=tail) {
u = dequeue();
// Search all adjacent white nodes v. If the capacity
// from u to v in the residual network is positive,
// enqueue v.
for (v=0; v<n+2; v++) {
if (color[v]==WHITE && capacity[u][v]-flow[u][v]>0) {
enqueue(v);
parent[v] = u;
}
}
}
// If the color of the target node is black now,
// it means that we reached it.
//printf("%d\n",color[target]);
return color[target]==BLACK;
}
// Ford-Fulkerson Algorithm
int max_flow (int source, int sink) {
int i,j,u;
// Initialize empty flow.
int max_flow = 0;
for (i=0; i<n+2; i++) {
for (j=0; j<n+2; j++) {
flow[i][j] = 0;
}
}
// While there exists an augmenting path,
// increment the flow along this path.
printf("\nAugmented Path :\n");
while (bfs(source,sink)) {
// Determine the amount by which we can increment the flow.
int increment = INFINITY;
for (u=sink; parent[u]!=(-1); u=parent[u]) {
increment = min(increment,capacity[parent[u]][u]-flow[parent[u]][u]);
}
//printf("\n%d\n",increment);
// Now increment the flow.
for (u=sink; parent[u]!=(-1); u=parent[u]) {
flow[parent[u]][u] += increment;
flow[u][parent[u]] -= increment; // Reverse in residual
}
printf("\t");
// Path trace
for (u=sink; parent[u]!=(-1); u=parent[u]) {
printf("%d<-",u);
}
printf("%d adds %d incremental flow\n",source,increment);
max_flow += increment;
//printf("\n\n%d %d\n\n",source,sink);
}
//printf("%d\n",s);
// No augmenting path anymore. We are done.
return max_flow;
}
// Reading the input file and the main program
int read_input_file() {
int a,b,i,j;
char filename[256] = {0};
printf("Enter data file name : ");
scanf("%s",&filename);
FILE* input = fopen(filename,"r");
if(!input){
printf("There was a problem opening file %s for reading.\n",filename);
return 0;
}
// read number of nodes and edges
fscanf(input,"%d %d",&n,&e);
// initialize empty capacity matrix
for (i=0; i<n+2; i++) {
for (j=0; j<n+2; j++) {
capacity[i][j] = 0;
}
}
// read edge capacities
for (i=0; i<e; i++) {
fscanf(input,"%d %d",&a,&b);
if(a==b){
printf("ERROR : Graph is not bipartite");
return 0;
}
capacity[a][b]= 1; // Could have parallel edges
}
fclose(input);
for(i=0;i<n/2;i++){
capacity[0][i+1]= 1;
capacity[i+6][n+1]= 1;
}
return 1;
}
//Extra works
/*void read_input_file_w() {
int a,b,c,i,j;
FILE* input = fopen(filename,"a+");
// read number of nodes and edges
fscanf(input,"%d %d",&n,&e);
// initialize empty capacity matrix
for (i=0; i<n+2; i++) {
for (j=0; j<n+2; j++) {
capacity[i][j] = 0;
}
}
// read edge capacities
for (i=0; i<e; i++) {
fscanf(input,"%d %d",&a,&b);
capacity[b][a]= 1; // Could have parallel edges
}
fclose(input);
for(i=0;i<n/2;i++){
capacity[0][i+6]= 1;
capacity[i+1][n+1]= 1;
}
}
void printMatrix(){
int i,j;
for (i=0; i<=n+1; i++) {
for (j=0; j<=n+1; j++) {
printf("%d ",capacity[i][j]);
}
printf("\n");
}
}*/
int start(){
int isBipartite=0;
while(!isBipartite){
printf("\n*******************************\n\tFind Stable Cuples\n*******************************\n");
isBipartite=read_input_file();
//printMatrix();
}
return isBipartite;
}
int main () {
int i,j;
int isBipartite=0;
isBipartite=start();
while(isBipartite){
int choice;
printf("\n*******************************\n\tFind Stable Cuples\n*******************************\n");
printf("Enter 1 : Find Optimal Solution\n");
printf("Enter 2 : Add New Data File\n");
printf("Enter 0 : Exit\n");
printf("\nEnter :");
scanf("%d",&choice);
if(choice==1){
printf("\ntotal flow is %d\n",max_flow(0,n+1));
printf("\nMatched couples:\n");
for (i=1; i<=n; i++)
//printf("%d ",parent[i]);
for (j=1; j<=n; j++)
if (flow[i][j]>0)
printf("\tMen:%d matched with Women:%d\n",i,j);
}else if(choice==2){
isBipartite=start();
//printMatrix();
}
else if(choice==0){
printf("Program Terminated\n");
exit(0);
}
else{
printf("Error : Wrong Input\n");
}
}
return 0;
}
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