Merge pull request #763 from harshbhagwani94/patch-1

Leetcode1786.cpp

Program's_Contributed_By_Contributors/C++ Programs/Leetcode1786.cpp

@@ -0,0 +1,56 @@
+//Leetcode-#1786. Number of Restricted Paths From First to Last Node - https://leetcode.com/problems/number-of-restricted-paths-from-first-to-last-node/
+
+#define pii pair<int, int>
+#define mod 1000000007
+class Solution {
+public:
+
+    void minimumDistanceUsingDijkstra(vector<pii> graph[], vector<int> &distanceFromLastNode, int n) {
+        priority_queue<pii, vector<pii>, greater<pii>> pq;
+        pq.push({0,n});
+        distanceFromLastNode[n] = 0;
+        while(!pq.empty()) {
+            int u = pq.top().second;
+            pq.pop();
+            for (auto edge : graph[u]) {
+                int v = edge.first, dis = edge.second;
+                if (distanceFromLastNode[v] > distanceFromLastNode[u] + dis) {
+                    distanceFromLastNode[v] = distanceFromLastNode[u] + dis;
+                    pq.push({distanceFromLastNode[v], v});
+                }
+            }
+        }
+    }
+
+    int dfs(vector<int> &path, vector<pii> graph[], vector<int> &distanceFromLastNode, int src) {
+        if (src==1)
+            return 1;
+
+        if(path[src]!=-1)
+            return path[src];
+
+        int ans=0;
+
+        for (auto edge : graph[src]) {
+            int v = edge.first;
+            if (distanceFromLastNode[v] > distanceFromLastNode[src]) {
+                ans = (ans%mod + dfs(path, graph, distanceFromLastNode, v))%mod;
+            }
+        }
+
+        return path[src]=ans;
+    }
+
+    int countRestrictedPaths(int n, vector<vector<int>>& edges) {
+        vector<pii> graph[n+1];
+        vector<int> distanceFromLastNode(n+1, INT_MAX);
+        for(auto edge : edges) {
+            graph[edge[0]].push_back({edge[1], edge[2]});
+            graph[edge[1]].push_back({edge[0], edge[2]});
+        }
+        minimumDistanceUsingDijkstra(graph, distanceFromLastNode, n);
+        vector<int> path(n+1, -1);
+        return dfs(path, graph, distanceFromLastNode, n );
+    }
+
+};