uva548-树

此题来自白书数据结构基础二叉树的训练参考

翻译请戳  http://luckycat.kshs.kh.edu.tw/

uva的翻译幸运猫里大部分有

解题思路

建树的思想跟白书里的是一样的，虽然此题给的是中序和后序遍历。

虽然节点最多有10000个，递归建树可能会栈溢出。。。但是依然AC了。。。

最后BFS整棵树就行啦。

代码

#include<stdio.h>
#define MAX_SIZE 10001
//#define LOCAL
typedef struct node {
    int value, tot;
    struct node *lchild, *rchild;
}Node;
int LOrder[MAX_SIZE], pL;
int MOrder[MAX_SIZE], pM;
Node *q[MAX_SIZE];
//char s[1000001];
bool ReadS()
{
    char ch;
    while((ch=getchar())==‘ ‘) ;
    if(ch==EOF) return false;
    while(ch != ‘\n‘) {
        ungetc(ch, stdin);
        int d;
        scanf("%d", &d);
        MOrder[++pM] = d;
        while((ch=getchar())==‘ ‘) ;
    }
    ch = getchar();
//    while(ch==‘ ‘) ch = getchar();
    while(ch != ‘\n‘) {
        ungetc(ch, stdin);
        int d;
        scanf("%d", &d);
        LOrder[++pL] = d;
        while((ch=getchar())==‘ ‘) ;
    }
    return true;
}
int FindRoot(int l, int r)
{
    for(int i=l; i<=r; i++) if(MOrder[i] == LOrder[pL]) return i;
}
void NewNode(Node *&root, int i)
{
    root = new Node;
    root->value = MOrder[i];
    root->tot = root->value;
    root->lchild = root->rchild = NULL;
}
void Build(Node *&root, int l, int r)
{
    if(l>r) { root = NULL; pL++; return ; }
    int i=FindRoot(l, r);
    NewNode(root, i);
    pL--;
    Build(root->rchild, i+1, r);
    pL--;
    Build(root->lchild, l, i-1);
}
void BFS(Node *root)
{
    int front, rear;
    Node* minNode;
    int minTot = 1e9;
    front = rear = MAX_SIZE - 1;
    rear = (rear+1) % MAX_SIZE;
    q[rear] = root;
    while(rear != front) {
        front=(front+1)%MAX_SIZE;
        if(q[front]->lchild != NULL) {
            rear=(rear+1)%MAX_SIZE;
            q[rear] = q[front]->lchild;
            q[rear]->tot += q[front]->tot;
            if(q[rear]->lchild==NULL&&q[rear]->rchild==NULL)
                if(q[rear]->tot < minTot)
                    { minNode = q[rear]; minTot = minNode->tot; }
        }
        if(q[front]->rchild != NULL) {
            rear=(rear+1)%MAX_SIZE;
            q[rear] = q[front]->rchild;
            q[rear]->tot += q[front]->tot;
            if(q[rear]->lchild==NULL&&q[rear]->rchild==NULL)
                if(q[rear]->tot < minTot)
                    { minNode = q[rear]; minTot = minNode->tot; }
        }
        if(q[front]->lchild==NULL&&q[front]->rchild==NULL&&q[front]->tot<minTot)
            { minNode = q[front]; minTot = minNode->tot; }
    }
    printf("%d\n", minNode->value);
}
int main()
{
    #ifdef LOCAL
        freopen("data.txt", "r", stdin);
        freopen("ans.txt", "w", stdout);
    #endif
    while(ReadS()) {
        Node *root = NULL;
        Build(root, 1, pL);
        BFS(root);
        pM = pL = 0;
    }
    return 0;
}