其实是存一下代码

1. AVL的java实现

维护一下每个点左右子树深度差，差绝对值大于2就转，转的方式和treap, splay转的方式差不多。旋转操作可以使两端差归零变得更平衡。

虽然平衡但转的次数太多反而慢了(?)，有空回来整理下，先咕着[旺柴]

  1 import java.util.*;
  2 class TestMain {
  3     public static void main(String[] args) {
  4         AvlTree mytree = new AvlTree();
  5         Scanner jdr = new Scanner(System.in);
  6         int t = jdr.nextInt();
  7         while(t > 0) {
  8             int opt = jdr.nextInt(), x = jdr.nextInt();
  9             switch (opt) {
 10                 case 1:
 11                     mytree.insert(x);
 12                     break;
 13                 case 2:
 14                     mytree.delete(x);
 15                     break;
 16                 case 3:
 17                     System.out.println(mytree.queryRank(x));
 18                     break;
 19                 case 4:
 20                     System.out.println(mytree.numAt(x));
 21                     break;
 22                 case 5:
 23                     System.out.println(mytree.queryPrev(x));
 24                     break;
 25                 case 6:
 26                     System.out.println(mytree.queryPost(x));
 27                     break;
 28             }
 29             t--;
 30         }
 31         jdr.close();
 32         return ;
 33     }
 34 }
 35 
 36 public class AvlTree {
 37     TreeNode root;
 38     static TreeNode buffer;
 39     AvlTree() {
 40         root = null;
 41     }
 42     public void insert(int x) {
 43         root = insert(root, null, x);
 44         return ;
 45     }
 46     public void delete(int x) {
 47         root = delete(root, null, x);
 48         return ;
 49     }
 50     public int queryRank(int x) {
 51         return queryRank(root, x);
 52     }
 53     public int numAt(int index) {
 54         return queryVal(root, index);
 55     }
 56     public int queryPrev(int x) {
 57         findPrev(root, x);
 58         return buffer.value;
 59     }
 60     public int queryPost(int x) {
 61         findPost(root, x);
 62         return buffer.value;
 63     }
 64     private static TreeNode insert(TreeNode node, TreeNode fa, int x) {
 65         if(node == null) return new TreeNode(x, fa);
 66         if(x < node.value) node.child[0] = insert(node.child[0], node, x);
 67         else if(node.value < x) node.child[1] = insert(node.child[1], node, x);
 68         else node.num ++;
 69         node.push_up();
 70         if(node.diff==-2 || node.diff==2) {
 71             int p = (node.diff + 2) / 4, q = -node.diff/2;
 72             if(node.child[p].diff == q)
 73                 node.child[p] = rotate(node.child[p], 1 - p);
 74             node = rotate(node, p);
 75         }
 76         return node;
 77     }
 78     private static TreeNode delete(TreeNode node, TreeNode fa, int x) {
 79         if(node == null) return null;
 80         if(x < node.value) node.child[0] = delete(node.child[0], node, x);
 81         else if(node.value < x) node.child[1] = delete(node.child[1], node, x);
 82         else {
 83             if(node.child[0]==null && node.child[1]==null) {
 84                 node.num --;
 85                 if(node.num == 0) return null;
 86             }else {
 87                 int p = (node.diff > 0) ? 1 : 0;
 88                 node = rotate(node, p);
 89                 node.child[1-p] = delete(node.child[1-p], node, x);    
 90             }
 91         }
 92         node.push_up();
 93         if(node.diff==-2 || node.diff==2) {
 94             int p = (node.diff + 2) / 4, q = -node.diff/2;
 95             if(node.child[p].diff == q)
 96                 node.child[p] = rotate(node.child[p], 1 - p);
 97             node = rotate(node, p);
 98         }
 99         return node;
100     }
101     private static TreeNode rotate(TreeNode node, int direction) {
102         int p = direction, q = 1 - direction;
103         TreeNode tmp = node.child[p];
104         node.child[p] = tmp.child[q];
105         tmp.child[q] = node;
106         tmp.father = node.father;
107         node.father = tmp;
108         node.push_up();
109         tmp.push_up();
110         return tmp;
111     }
112     private static int queryRank(TreeNode node, int x) {
113         if(node == null) return 0;
114         if(x < node.value)
115             return queryRank(node.child[0], x);
116         else if(node.value < x)    
117             return queryRank(node.child[1], x) + node.num + node.childWeight(0);
118         return node.childWeight(0) + 1;
119     }
120     private static int queryVal(TreeNode node, int index) {
121         if(node == null) return 0;
122         if(node.childWeight(0) >= index) 
123             return queryVal(node.child[0], index);
124         else if(node.childWeight(0) + node.num < index) 
125             return queryVal(node.child[1], index - node.childWeight(0) - node.num );
126         return node.value;
127     }
128     private static void findPrev(TreeNode node, int x) {
129         if(node == null) return ;
130         if(node.value < x) {
131             buffer = node;
132             findPrev(node.child[1], x);
133         }else findPrev(node.child[0], x);
134         return ;
135     }
136     private static void findPost(TreeNode node, int x) {
137         if(node == null) return ;
138         if(node.value > x) {
139             buffer = node;
140             findPost(node.child[0], x);
141         }else findPost(node.child[1], x);
142         return ;
143     }
144 }
145 class TreeNode {
146     int value, diff, height, num, weight;
147     TreeNode father;
148     TreeNode[] child;
149     TreeNode() {}
150     TreeNode(int x) {
151         value = x;
152         diff = 0;
153         num = 1;
154         weight = 1;
155         height = 0;
156         father = null;
157         child = new TreeNode[2];
158     }
159     TreeNode(int x, TreeNode fa) {
160         value = x;
161         diff = 0;
162         num = 1;
163         weight = 1;
164         height = 0;
165         father = fa;
166         child = new TreeNode[2];
167     }
168     public void push_up() {
169         int h1 = heightOf(child[1]), h0 = heightOf(child[0]);
170         height = max(h0, h1) + 1;
171         diff = h1 - h0;
172         weight = childWeight(0) + childWeight(1) + num;
173         return ;
174     }
175     public int childWeight(int i){
176         if(child[i] != null) return child[i].weight;
177         return 0;
178     }
179     private static int heightOf(TreeNode node) {
180         if(node != null) return node.height;
181         return -1;
182     }
183     private static int max(int x, int y){
184         if(x > y) return x;
185         return y;
186     }
187 }