Floyd-Warshall Algorithm

Resources:

গ্রাফ থিওরিতে হাতেখড়ি ১০: ফ্লয়েড ওয়ার্শল

CP-Algorithms

ইকরাম মাহমুদ

smilitude

Implementation:

	#include <bits/stdc++.h>
	using namespace std;
	#define INF 1<<30
	#define endl '\n'
	#define maxn 100005
	#define tc printf("Case %d: ", cs)
	#define tcn printf("Case %d:\n", cs);
	#define FASTIO ios_base::sync_with_stdio(false), cin.tie(0), cout.tie(0);
	typedef long long ll;
	const double PI = acos(-1.0);
	#define dbg1(x) cerr << #x << " = " << x << endl;
	#define dbg2(x, y) cerr << #x << " = " << x << ", " << #y << " = " << y << endl;
	#define dbg3(x, y, z) cerr << #x << " = " << x << ", " << #y << " = " << y << ", " << #z << " = " << z << endl;
	#define dbg4(w,x, y, z) cerr << #w << " = " << w << ", " <<#x << " = " << x << ", " << #y << " = " << y << ", " << #z << " = " << z << endl;
	template < typename F, typename S >
	ostream& operator << ( ostream& os, const pair< F, S > & p ) {
	return os << "(" << p.first << ", " << p.second << ")";
	}
	template < typename T >
	ostream &operator << ( ostream & os, const vector< T > &v ) {
	os << "{";
	for (auto it = v.begin(); it != v.end(); ++it) {
	if ( it != v.begin() ) os << ", ";
	os << *it;
	}
	return os << "}";
	}
	template < typename T >
	ostream &operator << ( ostream & os, const set< T > &v ) {
	os << "[";
	for (auto it = v.begin(); it != v.end(); ++it) {
	if ( it != v.begin()) os << ", ";
	os << *it;
	}
	return os << "]";
	}
	template < typename F, typename S >
	ostream &operator << ( ostream & os, const map< F, S > &v ) {
	os << "[";
	for (auto it = v.begin(); it != v.end(); ++it) {
	if ( it != v.begin() ) os << ", ";
	os << it -> first << " = " << it -> second ;
	}
	return os << "]";
	}
	#define dbg(args...) do {cerr << #args << " : "; faltu(args); } while(0)
	clock_t tStart = clock();
	#define timeStamp dbg("Execution Time: ", (double)(clock() - tStart)/CLOCKS_PER_SEC)
	void faltu () { cerr << endl; }
	template <typename T>
	void faltu( T a[], int n ) {
	for (int i = 0; i < n; ++i) cerr << a[i] << ' ';
	cerr << endl;
	}
	template <typename T, typename ... hello>
	void faltu( T arg, const hello &... rest) { cerr << arg << ' '; faltu(rest...); }
	// Program showing a policy-based data structure.
	#include <ext/pb_ds/assoc_container.hpp> // Common file
	#include <ext/pb_ds/tree_policy.hpp>
	#include <functional> // for less
	#include <iostream>
	using namespace __gnu_pbds;
	using namespace std;
	// GNU link : https://goo.gl/WVDL6g
	typedef tree<int, null_type, less_equal<int>, rb_tree_tag,
	tree_order_statistics_node_update>
	new_data_set;
	/**___________________________________________________**/
	int weight[101][101];
	const int inf = 1e9;
	int Node, Edge;
	void init()
	{
	for (int i = 1; i <= Node; i++)
	for (int j = 1; j <= Node; j++)
	weight[i][j] = inf;
	}
	void print()
	{
	for (int i = 1; i <= Node; i++) {
	for (int j = 1; j <= Node; j++) {
	if (weight[i][j] == inf)cout << setw(5) << "INF";
	//else if(i == j)cout <<setw(5)<< "0";
	else
	cout << setw(5) << weight[i][j];
	}
	cout << endl;
	//cout << endl;
	}
	}
	void warshall()
	{
	for (int k = 1; k <= Node; k++) {
	for (int i = 1; i <= Node; i++) {
	for (int j = 1; j <= Node; j++) {
	if (i == j)continue;
	if (weight[i][j] > weight[i][k] + weight[k][j]) {
	weight[i][j] = weight[i][k] + weight[k][j];
	}
	// print();
	//cout << "---------------\n";
	}
	}
	}
	}
	int main()
	{
	//FASTIO
	// /*
	#ifndef ONLINE_JUDGE
	freopen("in.txt", "r", stdin);
	freopen("out.txt", "w", stdout);
	freopen("error.txt", "w", stderr);
	#endif
	//*/
	cin >> Node >> Edge;
	init();
	for (int i = 1; i <= Edge; i++) {
	int u, v, cost;
	cin >> u >> v >> cost;
	weight[u][u] = 0;
	weight[v][v] = 0;
	weight[u][v] = cost;
	//weight[v][u] = cost;
	}
	// print();
	// cout << "--------------------------\n";
	warshall();
	//cout << "################################\n";
	print();
	}
	/*
	4 6
	4 1 20
	4 3 8
	3 2 5
	2 1 2
	1 2 3
	2 3 2
	*/

view raw warshall.cpp hosted with ❤ by GitHub

 

Problems:

B. Greg and Graph

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