Runtime: 10 ms (Top 100.0%) | Memory: 3.70 MB (Top 100.0%)

Author: AnasImloul

scripts/algorithms/N/Number of Ways to Arrive at Destination/Number of Ways to Arrive at Destination.rs

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+// Runtime: 10 ms (Top 100.0%) | Memory: 3.70 MB (Top 100.0%)
+
+use std::collections::*;
+
+const MOD:usize = 1_000_000_007;
+const INF:usize = 1_000_000_000_000_000;
+fn dfs(memo:&Vec<(usize,HashSet<usize>)>, dp:&mut Vec<usize>, i:usize) -> usize {
+  if dp[i] == INF {
+    let mut temp = 0;
+    for &j in &memo[i].1 {
+      temp += dfs(memo, dp, j);
+      temp %= MOD;
+    }
+    dp[i] = temp;
+  }
+
+  dp[i]
+}
+
+impl Solution {
+  pub fn count_paths(n: i32, roads: Vec<Vec<i32>>) -> i32 {
+    let n = n as usize;
+    let mut g = vec![vec![];n];
+    for arr in roads {
+      let a = arr[0] as usize;
+      let b = arr[1] as usize;
+      let c = arr[2] as usize;
+      g[a].push((b,c));
+      g[b].push((a,c));
+    }
+
+    
+    let mut memo = vec![(INF,HashSet::new());n];
+    memo[0].0 = 0;
+    let mut stack = vec![(0,0)];
+    while !stack.is_empty() {
+      let mut new_stack = vec![];
+      while let Some((ci,cv)) = stack.pop() {
+        for &(ni, v) in &g[ci] {
+          let nv = cv + v;
+          if nv < memo[ni].0 {
+            memo[ni].1 = HashSet::new();
+            memo[ni].1.insert(ci);
+            memo[ni].0 = nv;
+            new_stack.push((ni,nv));
+          } else if nv == memo[ni].0 {
+            memo[ni].1.insert(ci);
+          }
+        }
+      }
+      stack = new_stack;
+    }
+
+    let mut result = vec![INF;n];
+    result[0] = 1;
+    
+    dfs(&memo, &mut result, n-1) as i32
+  }
+}