Change id to index

Author: William Fiset

src/main/java/com/williamfiset/algorithms/graphtheory/treealgorithms/LowestCommonAncestorEulerTour.java

@@ -24,17 +24,17 @@ public static class TreeNode {
     // Number of nodes in the subtree. Computed when tree is built.
     private int n;
 
-    private int id;
+    private int index;
     private TreeNode parent;
     private List<TreeNode> children;
 
     // Useful constructor for root node.
-    public TreeNode(int id) {
-      this(id, /*parent=*/ null);
+    public TreeNode(int index) {
+      this(index, /*parent=*/ null);
     }
 
-    public TreeNode(int id, TreeNode parent) {
-      this.id = id;
+    public TreeNode(int index, TreeNode parent) {
+      this.index = index;
       this.parent = parent;
       children = new LinkedList<>();
     }
@@ -54,8 +54,8 @@ public int size() {
       return n;
     }
 
-    public int id() {
-      return id;
+    public int index() {
+      return index;
     }
 
     public TreeNode parent() {
@@ -79,9 +79,9 @@ public static TreeNode rootTree(List<List<Integer>> graph, int rootId) {
     // Do dfs to construct rooted tree.
     private static TreeNode buildTree(List<List<Integer>> graph, TreeNode node) {
       int subtreeNodeCount = 1;
-      for (int neighbor : graph.get(node.id())) {
+      for (int neighbor : graph.get(node.index())) {
         // Ignore adding an edge pointing back to parent.
-        if (node.parent() != null && neighbor == node.parent().id()) {
+        if (node.parent() != null && neighbor == node.parent().index()) {
           continue;
         }
 
@@ -97,14 +97,14 @@ private static TreeNode buildTree(List<List<Integer>> graph, TreeNode node) {
 
     @Override
     public String toString() {
-      return String.valueOf(id);
+      return String.valueOf(index);
     }
   }
 
   private final int n;
   private final TreeNode root;
 
-  private int index = 0;
+  private int tourIndex = 0;
   private boolean preprocessed;
 
   // Populated when constructing Euler Tour.
@@ -139,10 +139,10 @@ private void preprocess() {
   }
 
   private void visit(TreeNode node, long depth) {
-    nodeOrder[index] = node;
-    nodeDepth[index] = depth;
-    last[node.id()] = index;
-    index++;
+    nodeOrder[tourIndex] = node;
+    nodeDepth[tourIndex] = depth;
+    last[node.index()] = tourIndex;
+    tourIndex++;
   }
 
   // Construct Euler Tour by populating the 'depth' and 'nodeOrder' arrays.
@@ -323,19 +323,19 @@ private static void example1() {
 
     TreeNode lca = solver.lca(10, 15);
     System.out.printf("LCA of 10 and 15 = %s\n", lca);
-    if (lca.id() != 5) {
+    if (lca.index() != 5) {
       System.out.println("Error, expected lca to be 5");
     }
 
     lca = solver.lca(13, 14);
     System.out.printf("LCA of 13 and 14 = %s\n", lca);
-    if (lca.id() != 2) {
+    if (lca.index() != 2) {
       System.out.println("Error, expected lca to be 2");
     }
 
     lca = solver.lca(9, 11);
     System.out.printf("LCA of 9 and 11 = %s\n", lca);
-    if (lca.id() != 0) {
+    if (lca.index() != 0) {
       System.out.println("Error, expected lca to be 0");
     }
   }

src/test/java/com/williamfiset/algorithms/graphtheory/treealgorithms/LowestCommonAncestorEulerTourTest.java

@@ -35,21 +35,21 @@ private LowestCommonAncestorEulerTour.TreeNode createFirstTreeFromSlides() {
   public void testLcaTreeFromSlides1() {
     LowestCommonAncestorEulerTour.TreeNode root = createFirstTreeFromSlides();
     LowestCommonAncestorEulerTour fastSolver = new LowestCommonAncestorEulerTour(root);
-    assertThat(fastSolver.lca(14, 13).id()).isEqualTo(2);
-    assertThat(fastSolver.lca(10, 16).id()).isEqualTo(5);
-    assertThat(fastSolver.lca(9, 11).id()).isEqualTo(0);
+    assertThat(fastSolver.lca(14, 13).index()).isEqualTo(2);
+    assertThat(fastSolver.lca(10, 16).index()).isEqualTo(5);
+    assertThat(fastSolver.lca(9, 11).index()).isEqualTo(0);
   }
 
   @Test
   public void testLcaTreeFromSlides2() {
     LowestCommonAncestorEulerTour.TreeNode root = createFirstTreeFromSlides();
     LowestCommonAncestorEulerTour fastSolver = new LowestCommonAncestorEulerTour(root);
-    assertThat(fastSolver.lca(8, 9).id()).isEqualTo(3);
-    assertThat(fastSolver.lca(4, 8).id()).isEqualTo(1);
-    assertThat(fastSolver.lca(6, 13).id()).isEqualTo(2);
-    assertThat(fastSolver.lca(7, 13).id()).isEqualTo(7);
-    assertThat(fastSolver.lca(10, 5).id()).isEqualTo(5);
-    assertThat(fastSolver.lca(2, 16).id()).isEqualTo(2);
+    assertThat(fastSolver.lca(8, 9).index()).isEqualTo(3);
+    assertThat(fastSolver.lca(4, 8).index()).isEqualTo(1);
+    assertThat(fastSolver.lca(6, 13).index()).isEqualTo(2);
+    assertThat(fastSolver.lca(7, 13).index()).isEqualTo(7);
+    assertThat(fastSolver.lca(10, 5).index()).isEqualTo(5);
+    assertThat(fastSolver.lca(2, 16).index()).isEqualTo(2);
   }
 
   @Test
@@ -59,7 +59,7 @@ public void testLcaOfTheSameNodeIsItself() {
 
     // Try all nodes
     for (int id = 0; id < root.size(); id++) {
-      assertThat(fastSolver.lca(id, id).id()).isEqualTo(id);
+      assertThat(fastSolver.lca(id, id).index()).isEqualTo(id);
     }
   }
 
@@ -86,7 +86,7 @@ public void randomizedLcaQueriesVsOtherImpl() {
 
         assertThat(lca1).isNotNull();
         assertThat(lca2).isNotNull();
-        assertThat(lca1.id()).isEqualTo(lca2.id());
+        assertThat(lca1.id()).isEqualTo(lca2.index());
       }
     }
   }