Create NumberOfWaysToReachDestination.cpp

Graphs/NumberOfWaysToReachDestination.cpp

@@ -0,0 +1,48 @@
+class Solution {
+public:
+    int countPaths(int n, vector<vector<int>>& roads) {
+        int mod = (1e9 + 7);
+        vector<pair<int,int>> adj[n];
+        for(auto it: roads){
+            adj[it[0]].push_back({it[1], it[2]});
+            adj[it[1]].push_back({it[0], it[2]});
+        }
+
+        priority_queue<pair<long long,int>, vector<pair<long long,int>>, greater<pair<long long,int>>> pq;
+
+        vector<long long> dist(n, 1e18);
+        vector<int> ways(n, 0);
+
+        dist[0] = 0;
+        ways[0] = 1;
+
+        pq.push({0,0});
+
+
+        while(!pq.empty()){
+            long long dis = pq.top().first;
+            int node = pq.top().second;
+            pq.pop();
+
+            for(auto i : adj[node]){
+                int adjnode = i.first;
+                long long adjweight = i.second;
+
+                if(dis + adjweight < dist[adjnode]){
+                    dist[adjnode] = adjweight + dis;
+                    pq.push({dist[adjnode], adjnode});
+                    // IMP
+                    ways[adjnode] = ways[node]% mod;
+                    //
+                }
+                else if(dis + adjweight == dist[adjnode])
+                {
+                    // IMP
+                    ways[adjnode] = (ways[adjnode] + ways[node])%mod;
+                    //
+                }
+            }
+        }
+        return (ways[n - 1]) % mod;
+    }
+};