[Sicily][深搜]1156. Binary tree

最新推荐文章于 2016-12-02 10:58:35 发布

原创最新推荐文章于 2016-12-02 10:58:35 发布 · 546 阅读

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这道题我走了弯路，不需要用节点里的指针，可以直接记录序号。

此外，为了方便找到根节点，直接在节点里增加了记录parent信息的变量。

在网上查阅时，看到有人通过连续异或找到根节点的值，也算是技巧来的吧。

// Problem#: 1156
// Submission#: 4562912
// The source code is licensed under Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License
// URI: http://creativecommons.org/licenses/by-nc-sa/3.0/
// All Copyright reserved by Informatic Lab of Sun Yat-sen University
#include <iostream>
#include <cstring>
using namespace std;
struct Node {
    Node(int Num,int p) {
        key = '0';
        num = Num;
        left = NULL;
        right = NULL;
        parent = p;
    }
    Node(char k, int n, Node* l = NULL, Node* r = NULL,int p = -1) :key(k), num(n), left(l), right(r),parent(p) {}
    char key;
    int num;
    int parent;
    Node* left;
    Node* right;
};
int findRoot(Node* tree[]) {
    for (int i = 0; i < 1001; i++) {
        if (tree[i] != NULL) {
            Node* temp = tree[i];
            while (temp->parent != -1) {
                temp = tree[temp->parent];
            }
            return temp->num;
        }
    }
}
void PreOrder(Node* tree[], int flag) {
    std::cout << tree[flag]->key;
    if (tree[flag]->left != NULL) {
        PreOrder(tree, tree[flag]->left->num);
    }
    if (tree[flag]->right != NULL) {
        PreOrder(tree, tree[flag]->right->num);
    }
}
int main() {
    int num;
    Node* tree[1001];
    while ((cin >> num) && num != 'EOF') {
        memset(tree, NULL, sizeof(int*)*1001);
        for (int i = 0; i < num; i++) {
            int numOfNode, leftNum, RightNum;
            char keyOfNode;
            cin >> numOfNode >> keyOfNode >> leftNum >> RightNum;
            if (leftNum != 0 && tree[leftNum] == NULL) {
                tree[leftNum] = new  Node(leftNum,numOfNode);
                tree[leftNum]->parent = numOfNode;
            }
            else if (tree[leftNum] != NULL) {
                tree[leftNum]->parent = numOfNode;
            }
            if (RightNum != 0 && tree[RightNum] == NULL) {
                tree[RightNum] = new Node(RightNum,numOfNode);
                tree[RightNum]->parent = numOfNode;
            }
            else if (tree[RightNum] != NULL) {
                tree[RightNum]->parent = numOfNode;
            }
            if(tree[numOfNode]==NULL){
                tree[numOfNode] = new Node(keyOfNode, numOfNode, tree[leftNum], tree[RightNum]);
            }else {
                tree[numOfNode]->key = keyOfNode;
                tree[numOfNode]->left = tree[leftNum];
                tree[numOfNode]->right = tree[RightNum];
                tree[numOfNode]->num = numOfNode;
            }
        }
        int rootNum = findRoot(tree);
        PreOrder(tree, rootNum);
        std::cout << endl;
    }

    //system("PAUSE");
    return 0;
}