OpenJudge Cartesian Tree

【代码】

 #include <cstdio>
 #include <cstdlib>
 #include <cstring>
 #include <algorithm>
 using namespace std;

 const int maxn = ;
 //Tkey为输入主键与辅键的结构体
 //key表示主键，aux表示辅键，index表示是输入的第几个结点
 struct Tkey {
     int key, aux, index;
 } keys[maxn];
 //Tnode是BST结点的结构体，key表示主键，aux表示辅键
 //father表示父结点的编号，leftChild和rightChild表示左右儿子结点
 struct Tnode {
     int key, aux, father, leftChild, rightChild;
 } node[maxn];
 int n;

 //排序的比较函数
 bool cmp(const Tkey &a, const Tkey &b) {
     return a.key < b.key;
 }

 int main() {
     //读入数据
     int i;
     scanf("%d", &n);
     for (i = ; i <= n; ++i) {
         scanf("%d%d", &keys[i].key, &keys[i].aux);
         keys[i].index = i;
     }

     //按key对结点排序
     sort(keys + , keys + n + , cmp);

     //按key从小到大将结点插入BST
     //father表示当前插入结点的父节点，leftChild表示当前插入结点的左儿子节点
     //rightMost表示每次插入前BST最右的结点
     int p, father, leftChild, rightMost = ;
     for (i = ; i <= n; ++i) {
         //寻找插入结点的父亲与左儿子
         leftChild = ; father = rightMost;
         while (father !=  && node[father].aux > keys[i].aux) {
             leftChild = father;
             father = node[father].father;
         }
         //将结点插入BST
         p = keys[i].index;
         node[p].key = keys[i].key;
         node[p].aux = keys[i].aux;
         node[p].father = father;
         node[p].leftChild = leftChild;
         node[p].rightChild = ;
         if (father != )
             node[father].rightChild = p;
         if (leftChild != )
             node[leftChild].father = p;
         rightMost = keys[i].index;
     }

     //输出答案
     printf("YES\n");
     for (i = ; i <= n; ++i)
         printf("%d %d %d\n", node[i].father, node[i].leftChild, node[i].rightChild);
     return ;
 }