Add solution #1976

Author: JoshCrozier

README.md

@@ -875,6 +875,7 @@
 1929|[Concatenation of Array](./1929-concatenation-of-array.js)|Easy|
 1930|[Unique Length-3 Palindromic Subsequences](./1930-unique-length-3-palindromic-subsequences.js)|Medium|
 1935|[Maximum Number of Words You Can Type](./1935-maximum-number-of-words-you-can-type.js)|Easy|
+1976|[Number of Ways to Arrive at Destination](./1976-number-of-ways-to-arrive-at-destination.js)|Medium|
 1980|[Find Unique Binary String](./1980-find-unique-binary-string.js)|Medium|
 1985|[Find the Kth Largest Integer in the Array](./1985-find-the-kth-largest-integer-in-the-array.js)|Medium|
 1996|[The Number of Weak Characters in the Game](./1996-the-number-of-weak-characters-in-the-game.js)|Medium|

solutions/1976-number-of-ways-to-arrive-at-destination.js

@@ -0,0 +1,60 @@
+/**
+ * 1976. Number of Ways to Arrive at Destination
+ * https://leetcode.com/problems/number-of-ways-to-arrive-at-destination/
+ * Difficulty: Medium
+ *
+ * You are in a city that consists of n intersections numbered from 0 to n - 1 with bi-directional
+ * roads between some intersections. The inputs are generated such that you can reach any
+ * intersection from any other intersection and that there is at most one road between any two
+ * intersections.
+ *
+ * You are given an integer n and a 2D integer array roads where roads[i] = [ui, vi, timei] means
+ * that there is a road between intersections ui and vi that takes timei minutes to travel. You
+ * want to know in how many ways you can travel from intersection 0 to intersection n - 1 in the
+ * shortest amount of time.
+ *
+ * Return the number of ways you can arrive at your destination in the shortest amount of time.
+ * Since the answer may be large, return it modulo 109 + 7.
+ */
+
+/**
+ * @param {number} n
+ * @param {number[][]} roads
+ * @return {number}
+ */
+var countPaths = function(n, roads) {
+  const MOD = 1e9 + 7;
+  const graph = Array.from({ length: n }, () => []);
+  const distances = new Array(n).fill(Infinity);
+  const ways = new Array(n).fill(0);
+
+  for (const [u, v, time] of roads) {
+    graph[u].push([v, time]);
+    graph[v].push([u, time]);
+  }
+
+  const queue = [[0, 0]];
+  distances[0] = 0;
+  ways[0] = 1;
+
+  while (queue.length) {
+    const [dist, node] = queue.shift();
+
+    if (dist > distances[node]) continue;
+
+    for (const [next, time] of graph[node]) {
+      const newDist = dist + time;
+
+      if (newDist < distances[next]) {
+        distances[next] = newDist;
+        ways[next] = ways[node];
+        queue.push([newDist, next]);
+        queue.sort((a, b) => a[0] - b[0]);
+      } else if (newDist === distances[next]) {
+        ways[next] = (ways[next] + ways[node]) % MOD;
+      }
+    }
+  }
+
+  return ways[n - 1];
+};