Create 1976. Number of Ways to Arrive at Destination (#749)

Author: Chayandas07

1976. Number of Ways to Arrive at Destination

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+class Solution {
+public:
+    vector<vector<pair<int,long long>>>graph;
+
+    int countPaths(int n, vector<vector<int>>& roads) {
+        
+        graph.resize(n);
+
+        for(vector<int>road : roads){
+            int u = road[0], v = road[1], time = road[2];
+            graph[u].push_back({v,time});
+            graph[v].push_back({u,time});
+        }
+
+        vector<long long>dist(n, LLONG_MAX);
+        vector<int>ways(n, 0);
+        priority_queue<pair<long long, int>, vector<pair<long long, int>>, greater<>> pq;
+
+        dist[0] = 0;
+        ways[0] = 1;
+        pq.push({0, 0});
+
+        while(!pq.empty()){
+            auto [currTime, node] = pq.top();
+            pq.pop();
+
+            if(currTime > dist[node]){
+                continue;
+            }
+
+            for(auto [nextNode, time] : graph[node]){
+                long long newTime = time + currTime;
+                if(newTime < dist[nextNode]){
+                    dist[nextNode] = newTime;
+                    ways[nextNode] = ways[node];
+                    pq.push({newTime, nextNode});
+                }else if(newTime == dist[nextNode]){
+                    ways[nextNode] = (ways[nextNode] + ways[node]) % 1000000007;
+                }
+            }
+        }
+
+        return ways[n - 1];
+    }
+};