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Commit 21e5f8e

Browse files
哈希表增加部分题目
1 parent ae17a4d commit 21e5f8e

6 files changed

+190
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lines changed

‎哈希表/299.猜数字游戏.cpp‎

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/*
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* @lc app=leetcode.cn id=299 lang=cpp
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*
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* [299] 猜数字游戏
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*/
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// @lc code=start
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class Solution {
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public:
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string getHint(string secret, string guess) {
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// 数字对了 - 数字和位置全对了
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// 1. 数字 位置全对了
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int count1 = 0;
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// 2. 数字对了,不论顺序
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int count2 = 0;
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vector<int> m1(10);
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vector<int> m2(10);
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int n = secret.size();
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for (int i = 0; i < n; i++) {
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if (secret[i] == guess[i])
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{
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count1++;
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}
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m1[secret[i] - '0']++;
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m2[guess[i] - '0']++;
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}
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for (size_t i = 0; i < 10; i++)
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{
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count2 += min(m1[i], m2[i]);
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}
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stringstream oss;
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oss << count1 << "A" << count2 - count1 << "B";
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return oss.str();
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}
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};
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// @lc code=end
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/*
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* @lc app=leetcode.cn id=347 lang=cpp
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*
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* [347] 前 K 个高频元素
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*/
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// @lc code=start
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class Solution {
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public:
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static bool cmp(const pair<int, int>& a, const pair<int, int>& b) {
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return a.second > b.second;
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}
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vector<int> topKFrequent(vector<int>& nums, int k) {
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// 记录num的出现次数
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unordered_map<int, int> counting;
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for (int a : nums) {
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counting[a]++;
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}
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// 小顶堆,前 k 个频次最高的num
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// &Solution::cmp 类型为 void (*ptr)(const pair<int, int>&, const pair<int, int>&)
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// decltype(&Solution::cmp) 获取Solution::cmp函数的声明类型
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priority_queue<pair<int, int>, vector<pair<int, int>>, decltype(&Solution::cmp)> heap(Solution::cmp);
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for (auto& kv : counting) {
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if (heap.size() < k)
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heap.push(kv);
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else if (heap.size() >= k && kv.second >= heap.top().second) {
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heap.push(kv);
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heap.pop();
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}
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}
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vector<int> ans;
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for (int i = 0; i < k; i++) {
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ans.push_back(heap.top().first);
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heap.pop();
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}
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return ans;
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}
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};
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// @lc code=end
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/*
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* @lc app=leetcode.cn id=387 lang=cpp
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*
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* [387] 字符串中的第一个唯一字符
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*/
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// @lc code=start
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class Solution {
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public:
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int firstUniqChar(string s) {
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vector<int> memo(255);
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for (char c : s) {
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memo[c]++;
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}
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for (int i = 0; i < s.size(); i++) {
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if (memo[s[i]] == 1) {
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return i;
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}
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}
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return -1;
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}
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};
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// @lc code=end
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‎哈希表/389.找不同.cpp‎

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/*
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* @lc app=leetcode.cn id=389 lang=cpp
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*
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* [389] 找不同
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*/
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// @lc code=start
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class Solution {
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public:
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char findTheDifference(string s, string t) {
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char ans = 0;
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for (char c : s) {
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ans = ans ^ c;
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}
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for (char c : t) {
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ans = ans ^ c;
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}
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return ans;
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}
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};
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// @lc code=end
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‎哈希表/409.最长回文串.cpp‎

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/*
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* @lc app=leetcode.cn id=409 lang=cpp
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*
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* [409] 最长回文串
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*/
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// @lc code=start
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class Solution {
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public:
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int longestPalindrome(string s) {
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// 双数一定能构造
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// 只能有一个单数
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int odd = 0;
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int ans = 0;
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unordered_map<char, int> memo;
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for (char c: s) {
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memo[c]++;
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}
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for (auto& kv : memo) {
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if (kv.second % 2 == 0) {
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ans += kv.second;
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} else {
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odd = 1;
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ans += kv.second - 1;
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}
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}
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return ans + odd;
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}
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};
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// @lc code=end
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/*
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* @lc app=leetcode.cn id=438 lang=cpp
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*
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* [438] 找到字符串中所有字母异位词
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*/
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// @lc code=start
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class Solution {
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public:
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vector<int> findAnagrams(string s, string p) {
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if (s.size() < p.size()) return {};
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int k = p.size();
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vector<int> mp(256);
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vector<int> ms(256);
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for (int i = 0; i < k; i++) {
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mp[p[i]]++;
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ms[s[i]]++;
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}
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vector<int> ans;
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if (mp == ms) ans.push_back(0);
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// 滑动窗口
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for (int i = k; i < s.size(); i++) {
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// 丢弃一个
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ms[s[i-k]]--;
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// 加入一个
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ms[s[i]]++;
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if (mp == ms) ans.push_back(i-k+1);
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}
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return ans;
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}
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};
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// @lc code=end
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