# Find Maximum Shortest Distance in Each Component of a Graph

Given an adjacency matrix **graph[][]** of a weighted graph consisting of **N** nodes and positive weights, the task for each connected component of the graph is to find the maximum among all possible shortest distances between every pair of nodes.

**Examples:**

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Input:

Output:8 0 11

Explanation: There are three components in the graph namely a, b, c. In component (a) the shortest paths are following:

- The shortest distance between 3 and 4 is 5 units.
- The shortest distance between 3 and 1 is 1+5=6 units.
- The shortest distance between 3 and 5 is 5+3=8 units.
- The shortest distance between 1 and 4 is 1 unit.
- The shortest distance between 1 and 5 is 1+3=4 units.
- The shortest distance between 4 and 5 is 3 units.

Out of these shortest distances:

The maximum shortest distance in component (a) is8 unitsbetween node 3 and node 5.

Similarly,

The maximum shortest distance in component (b) is0 units.

The maximum shortest distance in component (c) is11 unitsbetween nodes 2 and 6.

Input:

Output:7

Explanation:Since, there is only one component with 2 nodes having an edge between them of distance 7. Therefore, the answer will be 7.

**Approach:** This given problem can be solved by finding the connected components in the graph using DFS** **and store the components in a list of lists. Floyd Warshall’s Algorithm can be used to find all-pairs shortest paths in each connected component which is based on Dynamic Programming. After getting the shortest distances of all possible pairs in the graph, **find the maximum shortest distances for each and ****every component in the graph****.** Follow the steps below to solve the problem:

- Define a function
**maxInThisComponent(vector<int> component, vector<vector<int>> graph)**and perform the following steps:- Initialize the variable
**maxDistance**as**INT_MIN**and**n**as the size of the component. - Iterate over the range
**[0, n)**using the variable**i**and perform the following tasks:- Iterate over the range
**[i+1, n)**using the variable**j**and update the value of**maxDistance**as the maximum of**maxDistance**or**graph[component[i]][component[j]]**.

- Iterate over the range
- Return the value of
**maxDistance**as the answer.

- Initialize the variable
- Initialize a vector
**visited**of size**N**and initialize the values as**false**. - Initialize vectors, say
**components[][]**and**temp[]**to store each component of the graph. - Using
**Depth First Search(DFS)**find all the components and store them in the vector**components[][]**. - Now, call the function
**floydWarshall(graph, V)**to implement Floyd Warshall algorithm to find the shortest distance between all pairs of a component of a graph. - Initialize a vector
**result[]**to store the result. - Initialize the variable
**numOfComp**as the size of the vector**components[][].** - Iterate over the range
**[0, numOfComp)**using the variable**i**and call the function**maxInThisComponent(components[i], graph)**and store the value returned by it in the vector**result[]**. - After performing the above steps, print the values of the vector
**result[]**as the answer.

Below is the implementation of the above approach:

## C++

`// C++ program for the above approach` `#include <bits/stdc++.h>` `using` `namespace` `std;` `// Below dfs function will be used to` `// get the connected components of a` `// graph and stores all the connected` `// nodes in the vector component` `void` `dfs(` `int` `src, vector<` `bool` `>& visited,` ` ` `vector<vector<` `int` `> >& graph,` ` ` `vector<` `int` `>& component, ` `int` `N)` `{` ` ` `// Mark this vertex as visited` ` ` `visited[src] = ` `true` `;` ` ` `// Put this node in component vector` ` ` `component.push_back(src);` ` ` `// For all other vertices in graph` ` ` `for` `(` `int` `dest = 0; dest < N; dest++) {` ` ` `// If there is an edge between` ` ` `// src and dest i.e., the value` ` ` `// of graph[u][v]!=INT_MAX` ` ` `if` `(graph[src][dest] != INT_MAX) {` ` ` `// If we haven't visited dest` ` ` `// then recursively apply` ` ` `// dfs on dest` ` ` `if` `(!visited[dest])` ` ` `dfs(dest, visited, graph,` ` ` `component, N);` ` ` `}` ` ` `}` `}` `// Below is the Floyd Warshall Algorithm` `// which is based on Dynamic Programming` `void` `floydWarshall(` ` ` `vector<vector<` `int` `> >& graph, ` `int` `N)` `{` ` ` `// For every vertex of graph find` ` ` `// the shortest distance with` ` ` `// other vertices` ` ` `for` `(` `int` `k = 0; k < N; k++) {` ` ` `for` `(` `int` `i = 0; i < N; i++) {` ` ` `for` `(` `int` `j = 0; j < N; j++) {` ` ` `// Taking care of interger` ` ` `// overflow` ` ` `if` `(graph[i][k] != INT_MAX` ` ` `&& graph[k][j] != INT_MAX) {` ` ` `// Update distance between` ` ` `// vertex i and j if choosing` ` ` `// k as an intermediate vertex` ` ` `// make a shorter distance` ` ` `if` `(graph[i][k] + graph[k][j]` ` ` `< graph[i][j])` ` ` `graph[i][j]` ` ` `= graph[i][k] + graph[k][j];` ` ` `}` ` ` `}` ` ` `}` ` ` `}` `}` `// Function to find the maximum shortest` `// path distance in a component by checking` `// the shortest distances between all` `// possible pairs of nodes` `int` `maxInThisComponent(vector<` `int` `>& component,` ` ` `vector<vector<` `int` `> >& graph)` `{` ` ` `int` `maxDistance = INT_MIN;` ` ` `int` `n = component.size();` ` ` `for` `(` `int` `i = 0; i < n; i++) {` ` ` `for` `(` `int` `j = i + 1; j < n; j++) {` ` ` `maxDistance` ` ` `= max(maxDistance,` ` ` `graph[component[i]][component[j]]);` ` ` `}` ` ` `}` ` ` `// If the maxDistance is still INT_MIN` ` ` `// then return 0 because this component` ` ` `// has a single element` ` ` `return` `(maxDistance == INT_MIN` ` ` `? 0` ` ` `: maxDistance);` `}` `// Below function uses above two method` `// to get the maximum shortest distances` `// in each component of the graph the` `// function returns a vector, where each` `// element denotes maximum shortest path` `// distance for a component` `vector<` `int` `> maximumShortesDistances(` ` ` `vector<vector<` `int` `> >& graph, ` `int` `N)` `{` ` ` `// Find the connected components` ` ` `vector<` `bool` `> visited(N, ` `false` `);` ` ` `vector<vector<` `int` `> > components;` ` ` `// For storing the nodes in a` ` ` `// particular component` ` ` `vector<` `int` `> temp;` ` ` `// Now for each unvisited node run` ` ` `// the dfs to get the connected` ` ` `// component having this unvisited node` ` ` `for` `(` `int` `i = 0; i < N; i++) {` ` ` `if` `(!visited[i]) {` ` ` `// First of all clear the temp` ` ` `temp.clear();` ` ` `dfs(i, visited, graph, temp, N);` ` ` `components.push_back(temp);` ` ` `}` ` ` `}` ` ` `// Now for all-pair find the shortest` ` ` `// path distances using Floyd Warshall` ` ` `floydWarshall(graph, N);` ` ` `// Now for each component find the` ` ` `// maximum shortest distance and` ` ` `// store it in result` ` ` `vector<` `int` `> result;` ` ` `int` `numOfComp = components.size();` ` ` `int` `maxDistance;` ` ` `for` `(` `int` `i = 0; i < numOfComp; i++) {` ` ` `maxDistance` ` ` `= maxInThisComponent(components[i], graph);` ` ` `result.push_back(maxDistance);` ` ` `}` ` ` `return` `result;` `}` `// Driver Code` `int` `main()` `{` ` ` `int` `N = 8;` ` ` `const` `int` `inf = INT_MAX;` ` ` `// Adjacency Matrix for the first` ` ` `// graph in the examples` ` ` `vector<vector<` `int` `> > graph1 = {` ` ` `{ 0, inf, 9, inf, inf, inf, 3, inf },` ` ` `{ inf, 0, inf, 10, 1, 8, inf, inf },` ` ` `{ 9, inf, 0, inf, inf, inf, 11, inf },` ` ` `{ inf, 10, inf, 0, 5, 13, inf, inf },` ` ` `{ inf, 1, inf, 5, 0, 3, inf, inf },` ` ` `{ 8, inf, inf, 13, 3, 0, inf, inf },` ` ` `{ 3, inf, 11, inf, inf, inf, 0, inf },` ` ` `{ inf, inf, inf, inf, inf, inf, inf, 0 },` ` ` `};` ` ` `// Find the maximum shortest distances` ` ` `vector<` `int` `> result1` ` ` `= maximumShortesDistances(graph1, N);` ` ` `// Printing the maximum shortest path` ` ` `// distances for each components` ` ` `for` `(` `int` `mx1 : result1)` ` ` `cout << mx1 << ` `' '` `;` ` ` `return` `0;` `}` |

## Javascript

`<script>` `// Javascript program for the above approach` `// Below dfs function will be used to` `// get the connected components of a` `// graph and stores all the connected` `// nodes in the vector component` `function` `dfs(src, visited, graph, component, N)` `{` ` ` `// Mark this vertex as visited` ` ` `visited[src] = ` `true` `;` ` ` `// Put this node in component vector` ` ` `component.push(src);` ` ` `// For all other vertices in graph` ` ` `for` `(let dest = 0; dest < N; dest++)` ` ` `{` ` ` ` ` `// If there is an edge between` ` ` `// src and dest i.e., the value` ` ` `// of graph[u][v]!=INT_MAX` ` ` `if` `(graph[src][dest] != Number.MAX_SAFE_INTEGER)` ` ` `{` ` ` ` ` `// If we haven't visited dest` ` ` `// then recursively apply` ` ` `// dfs on dest` ` ` `if` `(!visited[dest]) dfs(dest, visited, graph, component, N);` ` ` `}` ` ` `}` `}` `// Below is the Floyd Warshall Algorithm` `// which is based on Dynamic Programming` `function` `floydWarshall(graph, N)` `{` ` ` `// For every vertex of graph find` ` ` `// the shortest distance with` ` ` `// other vertices` ` ` `for` `(let k = 0; k < N; k++)` ` ` `{` ` ` `for` `(let i = 0; i < N; i++)` ` ` `{` ` ` `for` `(let j = 0; j < N; j++)` ` ` `{` ` ` `// Taking care of interger` ` ` `// overflow` ` ` `if` `(graph[i][k] != Number.MAX_SAFE_INTEGER && graph[k][j] != Number.MAX_SAFE_INTEGER)` ` ` `{` ` ` ` ` `// Update distance between` ` ` `// vertex i and j if choosing` ` ` `// k as an intermediate vertex` ` ` `// make a shorter distance` ` ` `if` `(graph[i][k] + graph[k][j] < graph[i][j])` ` ` `graph[i][j] = graph[i][k] + graph[k][j];` ` ` `}` ` ` `}` ` ` `}` ` ` `}` `}` `// Function to find the maximum shortest` `// path distance in a component by checking` `// the shortest distances between all` `// possible pairs of nodes` `function` `maxInThisComponent(component, graph) {` ` ` `let maxDistance = Number.MIN_SAFE_INTEGER;` ` ` `let n = component.length;` ` ` `for` `(let i = 0; i < n; i++) {` ` ` `for` `(let j = i + 1; j < n; j++) {` ` ` `maxDistance = Math.max(maxDistance, graph[component[i]][component[j]]);` ` ` `}` ` ` `}` ` ` `// If the maxDistance is still INT_MIN` ` ` `// then return 0 because this component` ` ` `// has a single element` ` ` `return` `maxDistance == Number.MIN_SAFE_INTEGER ? 0 : maxDistance;` `}` `// Below function uses above two method` `// to get the maximum shortest distances` `// in each component of the graph the` `// function returns a vector, where each` `// element denotes maximum shortest path` `// distance for a component` `function` `maximumShortesDistances(graph, N) {` ` ` `// Find the connected components` ` ` `let visited = ` `new` `Array(N).fill(` `false` `);` ` ` `let components = ` `new` `Array();` ` ` `// For storing the nodes in a` ` ` `// particular component` ` ` `let temp = [];` ` ` `// Now for each unvisited node run` ` ` `// the dfs to get the connected` ` ` `// component having this unvisited node` ` ` `for` `(let i = 0; i < N; i++) {` ` ` `if` `(!visited[i]) {` ` ` `// First of all clear the temp` ` ` `temp = [];` ` ` `dfs(i, visited, graph, temp, N);` ` ` `components.push(temp);` ` ` `}` ` ` `}` ` ` `// Now for all-pair find the shortest` ` ` `// path distances using Floyd Warshall` ` ` `floydWarshall(graph, N);` ` ` `// Now for each component find the` ` ` `// maximum shortest distance and` ` ` `// store it in result` ` ` `let result = [];` ` ` `let numOfComp = components.length;` ` ` `let maxDistance;` ` ` `for` `(let i = 0; i < numOfComp; i++) {` ` ` `maxDistance = maxInThisComponent(components[i], graph);` ` ` `result.push(maxDistance);` ` ` `}` ` ` `return` `result;` `}` `// Driver Code` `let N = 8;` `const inf = Number.MAX_SAFE_INTEGER;` `// Adjacency Matrix for the first` `// graph in the examples` `let graph1 = [` ` ` `[0, inf, 9, inf, inf, inf, 3, inf],` ` ` `[inf, 0, inf, 10, 1, 8, inf, inf],` ` ` `[9, inf, 0, inf, inf, inf, 11, inf],` ` ` `[inf, 10, inf, 0, 5, 13, inf, inf],` ` ` `[inf, 1, inf, 5, 0, 3, inf, inf],` ` ` `[8, inf, inf, 13, 3, 0, inf, inf],` ` ` `[3, inf, 11, inf, inf, inf, 0, inf],` ` ` `[inf, inf, inf, inf, inf, inf, inf, 0],` `];` `// Find the maximum shortest distances` `let result1 = maximumShortesDistances(graph1, N);` `// Printing the maximum shortest path` `// distances for each components` `for` `(mx1 of result1) document.write(mx1 + ` `" "` `);` `// This code is contributed by gfgking.` `</script>` |

**Output**

11 8 0

**Time Complexity:** O(N^{3}), where** **N is the number of vertices in the graph.**Auxiliary Space:** O(N)