1 #include<stdio.h>
2 #include<math.h>
3 #define MAXN 1000
4 struct node{
5 int left,right,data,height,parent;
6 };
7 struct node a[MAXN];
8 int n;
9 void read();
10 void updateHeight(int x);
11 int getfactor(int x);
12 int getheight(int x);
13 void L(int x1,int x2);
14 void R(int x1,int x2);
15 int main(){
16 read();
17 printf("%d\n",a[a[0].data].data);
18 return 0;
19 }
20 void read(){
21 int i,data,pre,now;
22 scanf("%d",&n);
23 a[0].data = 0;
24 for(i=1;i<=n;i++){
25 a[i].left= -1;
26 a[i].right=-1;
27 a[i].height=0;
28 a[i].parent=-1;
29 }
30 for(i=1;i<=n;i++){
31 scanf("%d",&data);
32 if(a[0].data==0) {
33 a[0].data=i;
34 a[i].data = data;
35 }else{
36 a[i].data = data;
37 now = a[0].data;
38 while(now!=-1){
39 pre = now;
40 if(a[now].data>data){
41 now = a[now].left;
42 }
43 else if(a[now].data<data){
44 now = a[now].right;
45 }
46 else{
47 now = -1;
48 break;
49 }
50 }
51 if(a[pre].data < data) a[pre].right = i;
52 else if(a[pre].data > data) a[pre].left = i;
53 a[i].parent = pre;
54 updateHeight(pre);
55 }
56 }
57
58 }
59
60 int getheight(int x){
61 int lefth,righth;
62 if(a[x].left==-1) lefth = 0;
63 else lefth = a[a[x].left].height + 1;
64
65 if(a[x].right==-1) righth = 0;
66 else righth = a[a[x].right].height + 1;
67
68 if(lefth>righth) return lefth;
69 else return righth;
70 }
71
72 void L(int x1,int x2){ //左旋转
73 int temp,parent;
74 temp = a[x2].left;
75 parent = a[x1].parent;
76 a[x2].left=-1;
77 a[x1].right = temp;
78 if(parent!=-1){
79 if(a[parent].left==x1) a[parent].left = x2;
80 else a[parent].right = x2;
81 }
82 else{
83 a[0].data = x2;
84 }
85 a[x2].left = x1;
86 a[x2].parent = parent;
87 a[x1].parent = x2;
88 if(temp!=-1) a[temp].parent=x1;
89
90 //更改高度
91 a[x1].height = getheight(x1);
92 a[x2].height = getheight(x2);
93
94
95
96 }
97 void R(int x1,int x2){ //右旋转
98 int temp,parent;
99 parent = a[x1].parent;
100 temp = a[x2].right;
101 a[x2].right = -1;
102 a[x1].left = temp;
103 a[x2].right = x1;
104 if(parent!=-1){
105 if(a[parent].left==x1) a[parent].left = x2;
106 else a[parent].right=x2;
107
108 }else{
109 a[0].data = x2; //更改根结点
110 }
111 //更改父亲结点指向
112 a[x1].parent = x2;
113 a[x2].parent = parent;
114 if(temp!=-1) a[temp].parent=x1;
115
116 a[x1].height = getheight(x1);
117 a[x2].height = getheight(x2);
118
119 }
120
121 int getfactor(int x){
122 int left,right;
123 if(a[x].left!=-1) left = a[a[x].left].height +1;
124 else left = 0;
125 if(a[x].right!=-1) right = a[a[x].right].height +1;
126 else right = 0;
127 return (left-right);
128 }
129 void updateHeight(int x){
130 int t=x;
131 int lefth,righth;
132 while(x!=-1){
133 if(a[x].left==-1) lefth = 0;
134 else lefth = a[a[x].left].height + 1;
135
136 if(a[x].right==-1) righth=0;
137 else righth = a[a[x].right].height + 1;
138
139 if (lefth>righth)
140 a[x].height =lefth;
141 else a[x].height = righth;
142 x = a[x].parent;
143 }
144 x = t;
145 int now,next,next1,factor,factor1;
146 while(x!=-1){
147 //factor = a[a[x].left].height - a[a[x].right].height;
148 factor = getfactor(x);
149 if(factor==-2){ //右子树重
150
151 now = x;
152 next = a[x].right;
153 x = a[x].parent;
154 //factor1 = a[a[next].left].height - a[a[next].right].height;
155 factor1 = getfactor(next);
156 if(factor1==1) {
157 next1 = a[next].left;
158 R(next,next1);
159 next = next1;
160 L(now,next);
161 }
162 else if(factor1==-1){
163 L(now,next);
164 }
165 }
166 else if(factor==2){ // 左子树重
167 now = x;
168 next = a[x].left;
169 x = a[x].parent;
170 //factor1 = a[a[next].left].height - a[a[next].right].height;
171 factor1 = getfactor(next);
172 if(factor1==1) {
173 R(now,next);
174 }
175 else if(factor1==-1){
176 next1 = a[next].right;
177 L(next,next1);
178 next = next1;
179 R(now,next);
180 }
181 }
182 else x = a[x].parent;
183 }
184 }
