20240623 Finished

src/problem/mod.rs

@@ -156,3 +156,4 @@ mod p230_kth_smallest_element_in_a_bst;
 mod p98_validate_binary_search_tree;
 mod p200_number_of_islands;
 mod p130_surrounded_regions;
+mod p399_evaluate_division;

src/problem/p399_evaluate_division.rs

@@ -0,0 +1,122 @@
+/**
+ * [399] Evaluate Division
+ */
+pub struct Solution {}
+
+
+// submission codes start here
+use std::collections::HashMap;
+
+struct UnionFind {
+    parents : Vec<usize>,
+    weights : Vec<f64>
+}
+
+impl UnionFind {
+    fn new(n: usize) -> UnionFind {
+        let mut parents = Vec::with_capacity(n);
+        let mut weights = Vec::with_capacity(n);
+
+        for i in 0..n {
+            parents.push(i);
+            weights.push(1f64);
+        }
+
+        UnionFind {
+            parents,
+            weights
+        }
+    }
+
+    fn find(&mut self, x: usize) -> usize {
+        if self.parents[x] == x {
+            return x;
+        }
+
+        let origin = self.parents[x];
+        self.parents[x] = self.find(origin);
+        self.weights[x] *= self.weights[origin];
+        self.parents[x]
+    }
+
+    fn merge(&mut self, x: usize, y: usize, value: f64) {
+        let (x_root, y_root) = (self.find(x), self.find(y));
+
+        if x_root == y_root {
+            return;
+        }
+
+        self.parents[x_root] = y_root;
+        self.weights[x_root] = value * self.weights[y] / self.weights[x];
+    }
+
+    fn is_connected(&mut self, x: usize, y: usize) -> f64 {
+        let (x_root, y_root) = (self.find(x), self.find(y));
+
+        if x_root == y_root {
+            return self.weights[x] / self.weights[y];
+        }
+
+        -1f64
+    }
+}
+
+impl Solution {
+    pub fn calc_equation(equations: Vec<Vec<String>>, values: Vec<f64>, queries: Vec<Vec<String>>) -> Vec<f64> {
+        let count = equations.len();
+        let mut union_find = UnionFind::new(count * 2);
+        let mut id_map = HashMap::with_capacity(count * 2);
+        let mut id = 0;
+
+        for (i, equation) in equations.iter().enumerate() {
+            let (x, y) = (&equation[0], &equation[1]);
+            
+            let x_id = *id_map.entry(x).or_insert_with(|| {
+                let inserted_id = id;
+                id += 1;
+                inserted_id
+            });
+
+            let y_id = *id_map.entry(y).or_insert_with(|| {
+                let inserted_id = id;
+                id += 1;
+                inserted_id
+            });
+
+            union_find.merge(x_id, y_id, values[i]);
+        }
+
+        let mut result = Vec::with_capacity(queries.len());
+        for query in &queries {
+            let (x, y) = (&query[0], &query[1]);
+
+            let (x_id, y_id) = (id_map.get(x), id_map.get(y));
+
+            if x_id.is_none() || y_id.is_none() {
+                result.push(-1f64);
+            } else {
+                result.push(union_find.is_connected(*x_id.unwrap(),*y_id.unwrap()));
+            }
+        }
+    
+        result
+    }
+}
+
+// submission codes end
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_399() {
+        let mut map = HashMap::new();
+        let x = "a".to_owned();
+        let y = "a".to_owned();
+
+        map.entry(&x).or_insert(1);
+
+        assert_eq!(map.get(&y), Some(&1));
+    }
+}