1110. Complete Binary Tree 解析

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刚开始像之前那个题一样，看到只有20个结点，想着不大，丢到数组里面看有没有空结点。发现不对。。。

后面改了方法，用广度遍历，遍历到空结点的时候，看看是不是所有结点都遍历完了，来判断。

注意输入的时候，不要像我一样用char在读入。数字有两位的。。哎。。。

#include <iostream>#include <cstring>#include <queue>#include <string>#define MAX 25#define null -1using namespace std;struct Node {int left;int right;};Node Tree[MAX];bool isVis[MAX];vector <int> tempNode;int n;int last = 0;bool Check(int root) {queue <int> q;bool isEmpty = false;if (root == null)return true;q.push(root);tempNode.push_back(root);while (!q.empty()) {int temp = q.front();q.pop();last = temp;if (Tree[temp].left == null) {break;}else {q.push(Tree[temp].left);tempNode.push_back(Tree[temp].left);}if (Tree[temp].right == null) {break;}else {q.push(Tree[temp].right);tempNode.push_back(Tree[temp].right);}}if (tempNode.size() != n)return false;return true;}int str2int(string s) {int sum = 0;for (int i = 0; i < s.size(); i++) {sum *= 10;sum += s[i] - '0';}return sum;}int main() {cin >> n;memset(isVis, false, sizeof(isVis));string temp1, temp2;for (int i = 0; i < n; i++) {cin >> temp1 >> temp2;//cout << temp1 << temp2 << endl;if (temp1[0] == '-')Tree[i].left = null;else {Tree[i].left = str2int(temp1);isVis[Tree[i].left] = true;}if (temp2[0] == '-')Tree[i].right = null;else {Tree[i].right = str2int(temp2);isVis[Tree[i].right] = true;}}int root = null;for (int i = 0; i < n; i++) {if (!isVis[i]) {root = i;break;}}bool isCT = Check(root);if (isCT)cout << "YES " << tempNode[n-1] << endl;elsecout << "NO " << root << endl;return 0;}

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