PAT 1099 Build A Binary Search Tree

题意：

依次给出各点的左右孩子结点号， 接着再往其中存入一组数字。要求构成二叉搜索树。

注意点：

1. 理解题目含义。 构建树时，给的输入是0~n各点各自的左右孩子，而非我之前理解的用先序遍历存入的孩子信息。

2. 注意加上-1的判断。

//628K94MS#include<cstdio>#include<algorithm>#include<cstring>#include<iostream>#include<stack>#include<vector>#include<queue>using namespace std;#define inf 0x3f3f3f3f#define M 2500int lchild[M],rchild[M];int n;void BuildTree(){int l,r;for(int i = 0 ;i < n; i++){scanf("%d%d",&l,&r);lchild[i] = l;rchild[i] = r;}}int k;int num[M],ans[M];void InsertTree(int node){if(node == -1 || k >= n)return ;InsertTree(lchild[node]);ans[node] = num[k++];InsertTree(rchild[node]);}void printTree(int node){queue<int> q;q.push(node);printf("%d",ans[node]);while(!q.empty()){node = q.front();q.pop();if(node != 0)printf(" %d", ans[node]);if(lchild[node] != -1)q.push(lchild[node]);if(rchild[node] != -1)q.push(rchild[node]);}cout<<endl;}int main(){scanf("%d",&n);if(n == 0)return 0;BuildTree();for(int i = 0;i < n; i++){scanf("%d",&num[i]);}sort(num,num+n);k = 0;InsertTree(0);printTree(0);return 0;}