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501.二叉搜索树中的众数.cpp
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501.二叉搜索树中的众数.cpp
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#include <map>
#include <unordered_map>
#include <set>
#include <unordered_set>
#include <queue>
#include <stack>
#include <deque>
#include <list>
#include <string>
#include <algorithm>
#include <iterator>
using namespace std;
/*
* @lc app=leetcode.cn id=501 lang=cpp
*
* [501] 二叉搜索树中的众数
*/
struct TreeNode
{
int val;
TreeNode *left;
TreeNode *right;
TreeNode() : val(0), left(nullptr), right(nullptr) {}
TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
};
// @lc code=start
/**
* Definition for a binary tree node.
* struct TreeNode {
* int val;
* TreeNode *left;
* TreeNode *right;
* TreeNode() : val(0), left(nullptr), right(nullptr) {}
* TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
* TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
* };
*/
class Solution {
public:
//递归法
int maxCount = 0;
int count = 0;
vector<int> result;
TreeNode* pre = NULL;
void inorder(TreeNode* root) {
if (root == NULL) {
return;
}
inorder(root->left);
if (pre == NULL) {
count = 1;
} else if (pre->val == root->val) {
count++;
} else {
count = 1;
}
pre = root;
if (count == maxCount) {
result.push_back(root->val);
} else if (count > maxCount) {
maxCount = count;
result.clear();
result.push_back(root->val);
}
inorder(root->right);
return;
}
vector<int> findMode(TreeNode* root) {
result.clear();
inorder(root);
return result;
}
//迭代法,中序
vector<int> findMode_1(TreeNode* root) {
int maxCount = 0;
int count = 0;
vector<int> result;
stack<TreeNode*> ts;
TreeNode* pre = NULL;
TreeNode* cur = root;
while (cur != NULL || ts.empty() != 1) {
if (cur != NULL) {
ts.push(cur);
cur = cur->left;
} else {
cur = ts.top();
ts.pop();
if (pre == NULL) {
count = 1;
} else if (pre->val == cur->val) {
++count;
} else {
count = 1;
}
if (count == maxCount) {
result.push_back(cur->val);
} else if (count > maxCount) {
result.clear();
maxCount = count;
result.push_back(cur->val);
}
pre = cur;
cur = cur->right;
}
}
return result;
}
};
// @lc code=end