Data commit

Task/AVL-tree/JavaScript/avl-tree-1.js

@@ -0,0 +1,91 @@
+function tree(less, val, more) {
+  return {
+    depth: 1+Math.max(less.depth, more.depth),
+    less: less,
+    val: val,
+    more: more,
+  };
+}
+
+function node(val) {
+  return tree({depth: 0}, val, {depth: 0});
+}
+
+function insert(x,y) {
+  if (0 == y.depth) return x;
+  if (0 == x.depth) return y;
+  if (1 == x.depth && 1 == y.depth) {
+    switch (Math.sign(y.val)-x.val) {
+      case -1: return tree(y, x.val, {depth: 0});
+      case 0: return y;
+      case 1: return tree(x, y.val, {depth: 0});
+    }
+  }
+  switch (Math.sign(y.val-x.val)) {
+    case -1: return balance(insert(x.less, y), x.val, x.more);
+    case 0: return balance(insert(x.less, y.less), x.val, insert(x.more, y.more));
+    case 1: return balance(x.less. x.val, insert(x.more, y));
+  }
+}
+
+function balance(less,val,more) {
+  if (2 > Math.abs(less.depth-more.depth))
+    return tree(less,val,more);
+  if (more.depth > less.depth) {
+    if (more.more.depth >= more.less.depth) {
+      // 'more' was heavy
+      return moreHeavy(less, val, more);
+    } else {
+      return moreHeavy(less,val,lessHeavy(more.less, more.val, more.more));
+    }
+  } else {
+    if(less.less.depth >= less.more.depth) {
+      return lessHeavy(less, val, more);
+    } else {
+      return lessHeavy(moreHeavy(less.less, less.val, less.more), val, more);
+    }
+  }
+}
+
+function moreHeavy(less,val,more) {
+  return tree(tree(less,val,more.less), more.val, more.more)
+}
+
+function lessHeavy(less,val,more) {
+  return tree(less.less, less.val, tree(less.more, val, more));
+}
+
+function remove(val, y) {
+  switch (y.depth) {
+    case 0: return y;
+    case 1:
+      if (val == y.val) {
+        return y.less;
+      } else {
+        return y;
+      }
+    default:
+      switch (Math.sign(y.val - val)) {
+        case -1: return balance(y.less, y.val, remove(val, y.more));
+        case  0: return insert(y.less, y.more);
+        case  1: return balance(remove(val, y.less), y.val, y.more)
+      }
+  }
+}
+
+function lookup(val, y) {
+  switch (y.depth) {
+    case 0: return y;
+    case 1: if (val == y.val) {
+      return y;
+    } else {
+      return {depth: 0};
+    }
+    default:
+      switch (Math.sign(y.val-val)) {
+        case -1: return lookup(val, y.more);
+        case  0: return y;
+        case  1: return lookup(val, y.less);
+      }
+  }
+}

Task/AVL-tree/JavaScript/avl-tree-2.js

@@ -0,0 +1,20 @@
+function dumptree(t) {
+  switch (t.depth) {
+    case 0: return '';
+    case 1: return t.val;
+    default: return '('+dumptree(t.less)+','+t.val+','+dumptree(t.more)+')';
+  }
+}
+function example() {
+  let t= node(0);
+  for (let j= 1; j<20; j++) {
+    t= insert(node(j), t);
+  }
+  console.log(dumptree(t));
+  t= remove(2, t);
+  console.log(dumptree(t));
+  console.log(dumptree(lookup(5, t)));
+  console.log(dumptree(remove(5, t)));
+}
+
+example();