Create Floyd_Warshall.cpp

Program's_Contributed_By_Contributors/C++/Floyd_Warshall.cpp

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+// C++ Program for Floyd Warshall Algorithm
+#include <bits/stdc++.h>
+using namespace std;
+
+// Number of vertices in the graph
+#define V 4
+
+/* Define Infinite as a large enough
+value.This value will be used for
+vertices not connected to each other */
+#define INF 99999
+
+// A function to print the solution matrix
+void printSolution(int dist[][V]);
+
+// Solves the all-pairs shortest path
+// problem using Floyd Warshall algorithm
+void floydWarshall(int graph[][V])
+{
+    /* dist[][] will be the output matrix
+    that will finally have the shortest
+    distances between every pair of vertices */
+    int dist[V][V], i, j, k;
+
+    /* Initialize the solution matrix same
+    as input graph matrix. Or we can say
+    the initial values of shortest distances
+    are based on shortest paths considering
+    no intermediate vertex. */
+    for (i = 0; i < V; i++)
+        for (j = 0; j < V; j++)
+            dist[i][j] = graph[i][j];
+
+    /* Add all vertices one by one to
+    the set of intermediate vertices.
+    ---> Before start of an iteration,
+    we have shortest distances between all
+    pairs of vertices such that the
+    shortest distances consider only the
+    vertices in set {0, 1, 2, .. k-1} as
+    intermediate vertices.
+    ----> After the end of an iteration,
+    vertex no. k is added to the set of
+    intermediate vertices and the set becomes {0, 1, 2, ..
+    k} */
+    for (k = 0; k < V; k++) {
+        // Pick all vertices as source one by one
+        for (i = 0; i < V; i++) {
+            // Pick all vertices as destination for the
+            // above picked source
+            for (j = 0; j < V; j++) {
+                // If vertex k is on the shortest path from
+                // i to j, then update the value of
+                // dist[i][j]
+                if (dist[i][j] > (dist[i][k] + dist[k][j])
+                    && (dist[k][j] != INF
+                        && dist[i][k] != INF))
+                    dist[i][j] = dist[i][k] + dist[k][j];
+            }
+        }
+    }
+
+    // Print the shortest distance matrix
+    printSolution(dist);
+}
+
+/* A utility function to print solution */
+void printSolution(int dist[][V])
+{
+    cout << "The following matrix shows the shortest "
+            "distances"
+            " between every pair of vertices \n";
+    for (int i = 0; i < V; i++) {
+        for (int j = 0; j < V; j++) {
+            if (dist[i][j] == INF)
+                cout << "INF"
+                     << "     ";
+            else
+                cout << dist[i][j] << "     ";
+        }
+        cout << endl;
+    }
+}
+
+// Driver's code
+int main()
+{
+    int graph[V][V] = { { 0, 5, INF, 10 },
+                        { INF, 0, 3, INF },
+                        { INF, INF, 0, 1 },
+                        { INF, INF, INF, 0 } };
+
+    // Function call
+    floydWarshall(graph);
+    return 0;
+}