shitu13

// Approach 1
// Complexity: O(n*log n)
class Solution {
public:
    vector<int> countBits(int n) {
        vector<int> ans;

        for(int i=0; i<=n; i++){
            ans.push_back(__builtin_popcount(i));
        }

shitu13

class Solution {
public:
    int longestPalindrome(string s) {
        unordered_map<int, int> mp;

        for (char& ch : s)
            mp[ch]++;

        bool odd_cnt = false;
        int res = 0;

shitu13

int search(vector<int> &nums, int target) {
    // Write your code here.

    int start =0;
    int end = nums.size()-1;
    int mid = start+(end-start)/2;

    while(start<=end){
        if(nums[mid]==target)
        return mid;

shitu13

class Solution {
public:
    vector<int> intersection(vector<int>& nums1, vector<int>& nums2) {
        unordered_set<int> uset(nums1.begin(), nums1.end());
        vector<int> res;

        for (int& num : nums2) {
            if (uset.find(num) != uset.end()) {
                res.push_back(num);
                uset.erase(num);

shitu13

class Solution {
public:
    vector<int> targetIndices(vector<int>& nums, int target) {
        sort(nums.begin(), nums.end());

        int n = nums.size();
        vector<int> res;

        for (int i = 0; i < n; i++) {
            if (nums[i] == target)

shitu13

// Approach 1
// Complexity: O(n^2)

class Solution {
public:
    int countPairs(vector<int>& nums, int target) {
        int result = 0;
        for(int i=0; i<nums.size(); i++){
            for(int j=i+1; j<nums.size();j++){
            if(nums[i]+nums[j]<target){

shitu13

class Solution {
public:
    vector<string> summaryRanges(vector<int>& nums) {
        int n = nums.size();
        vector<string> res;


        for (int i = 0; i < n; i++) {
            int start = nums[i];

shitu13

class Solution {
public:
    bool isArraySpecial(vector<int>& nums) {
        int n = nums.size();

        if (n == 1)
            return true;

        for (int i = 0; i < n - 1; i += 1) {
            if (nums[i] % 2 == 0 && nums[i + 1] % 2 != 0)

shitu13

// With memorization
class Solution {
private:
    int t[101];
    int solve(vector<int>& nums, int idx, int& n) {
        if (idx >= n)
            return 0;

        if (t[idx] != -1) {
            return t[idx];

shitu13

class Solution {
public:
    vector<int> rightSideView(TreeNode* root) {
        vector<int> res;

        if (root == NULL)
            return {};

        queue<TreeNode*> que;
        que.push(root);