#include <bits/stdc++.h>
using namespace std;
// Function to perform beam search
void beamSearch(map<char, map<char, int>> graph, char start, char goal, int beamWidth, map<char, int>& heuristics) {
// Priority queue to hold paths with cumulative cost and their respective nodes
priority_queue<pair<int, vector<char>>, vector<pair<int, vector<char>>>, greater<pair<int, vector<char>>>> currentLevel;
currentLevel.push({heuristics[start], {start}}); // Start path with heuristic value
while (!currentLevel.empty()) {
vector<pair<int, vector<char>>> nextLevel;
// Process all paths in the current level
int currentLevelSize = currentLevel.size();
for (int i = 0; i < currentLevelSize; i++) {
int currentCost = currentLevel.top().first;
vector<char> currentPath = currentLevel.top().second;
currentLevel.pop();
// Get the current node (last node in the path)
char currentNode = currentPath.back();
cout << "Current path: ";
for (char node : currentPath) cout << node << " ";
cout << "| Cost: " << currentCost << endl;
// Check if goal is reached
if (currentNode == goal) {
cout << "Path found: ";
for (char node : currentPath) cout << node << " ";
cout << "| Cost: " << currentCost << endl;
return;
}
// Explore neighbors of the current node
cout << "Processing node: " << currentNode << endl;
for (auto neighbor : graph[currentNode]) {
char nextNode = neighbor.first;
int edgeCost = neighbor.second;
// Avoid revisiting nodes in the current path
if (find(currentPath.begin(), currentPath.end(), nextNode) == currentPath.end()) {
// Mark as visited
// Create a new path and calculate its cost
vector<char> newPath = currentPath;
newPath.push_back(nextNode);
int newCost = currentCost + edgeCost + heuristics[nextNode];
cout << "| New Cost: " << newCost << " for " << nextNode << endl;
// Add the new path to the next level
nextLevel.push_back({newCost, newPath});
}
}
}
// Sort all paths at this level by cost and keep only the best `beamWidth` paths
sort(nextLevel.begin(), nextLevel.end());
for (int i = 0; i < min(beamWidth, (int)nextLevel.size()); i++) {
currentLevel.push(nextLevel[i]);
}
}
// If no path to the goal was found
cout << "No path found to the goal." << endl;
}
int main() {
// Define the graph as adjacency lists with edge costs
map<char, map<char, int>> graph = {
{'S', {{'A', 3}, {'B', 5}}},
{'A', {{'S', 3}, {'B', 4}, {'D', 3}}},
{'B', {{'S', 5}, {'A', 4}, {'C', 4}}},
{'C', {{'B', 4}, {'E', 6}}},
{'D', {{'A', 3}, {'G', 5}}},
{'E', {{'C', 6}}},
{'G', {{'D', 5}}}
};
// Define heuristic values for each node to the goal 'G'
map<char, int> heuristics;
heuristics['S'] = 10;
heuristics['A'] = 9;
heuristics['B'] = 8;
heuristics['C'] = 7;
heuristics['D'] = 6;
heuristics['E'] = 5;
heuristics['G'] = 0;
unordered_map<char, int> vis;
// Beam search with a beam width of 2
beamSearch(graph, 'S', 'G', 3, heuristics);
return 0;
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C++ is a widely used middle-level programming language.
When ever you want to perform a set of operations based on a condition If-Else is used.
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You can also use if-else for nested Ifs and If-Else-If ladder when multiple conditions are to be performed on a single variable.
Switch is an alternative to If-Else-If ladder.
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......
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For loop is used to iterate a set of statements based on a condition.
for(Initialization; Condition; Increment/decrement){
//code
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While is also used to iterate a set of statements based on a condition. Usually while is preferred when number of iterations are not known in advance.
while (condition) {
// code
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Do-while is also used to iterate a set of statements based on a condition. It is mostly used when you need to execute the statements atleast once.
do {
// code
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Function is a sub-routine which contains set of statements. Usually functions are written when multiple calls are required to same set of statements which increases re-usuability and modularity. Function gets run only when it is called.
return_type function_name(parameters);
function_name (parameters)
return_type function_name(parameters) {
// code
}