xzhang311

class Solution {
public:
    int countBattleships(vector<vector<char>>& board) {
        int res = 0;
        
        for(int i=0; i<board.size(); i++){
            for(int j=0; j<board[0].size(); j++){
                if((i-1<0||board[i-1][j]=='.')&&(j-1<0||board[i][j-1]=='.')&&board[i][j]=='X')
                    res++;
            }

xzhang311

class Solution {
public:
    int hammingDistance(int x, int y) {
        int z = x^y;
        
        int c=0;
        while(z!=0){
            z= (z-1)&z;
            c++;
        }

xzhang311

class Solution {
public:
    int lengthLongestPath(string s) {
        vector<int> lvls(128, 0);
        int res = 0;
        int cur_len = 0;
        int i=0;
        int ss=0;
        bool met_file=false;
        while(i<s.length()){

xzhang311

class Solution {
public:
    int getSum(int a, int b) {
        int res = 0;
        while(b!=0){
            int _a = a^b;
            int _b = (a&b)<<1;
            a = _a;
            b = _b;
            res = a|b;

xzhang311

class Solution {
public:
    int helper(int n, vector<int>& p){
        if(n<0) return 0;

        if(p[n]!=0)
            return p[n];
            
        p[n]=helper(n-1, p)+helper(n-2, p);
        return p[n];

xzhang311

vector<int> grayCode(int n) 
{         
    vector<int> result(1, 0);        
    for (int i = 0; i < n; i++) {
        int curCount = result.size();
        // push back all element in result in reverse order
        while (curCount) {
            curCount--;
            int curNum = result[curCount];
            curNum += (1<<i);

xzhang311

    int lengthOfLongestSubstringTwoDistinct(string s) {
        int res=0;
        if(s.empty())
            return res;
        unordered_map<char, int> myMap;
        int p0=0, p1=0;
        int count = 0;
        while(p1<s.length()){
            char c = s[p1];
            myMap[c]++;

xzhang311

class Solution {
public:
    int maximumGap(vector<int>& nums) {
        if(nums.size()<2)
            return 0;
        vector<vector<int> > curBucket(10);
        vector<int> curNums=nums;
        
        for(int i=0; i<32; i++){
            for(int j=0; j<curNums.size(); j++){

xzhang311

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {

xzhang311

class Solution {
public:
    void helper(vector<vector<char>>& grid, int row, int col){
        if(row<0||col<0||row>=grid.size()||col>=grid[0].size()||grid[row][col]=='0')
            return;
            
        grid[row][col]='0';
        helper(grid, row, col-1);
        helper(grid, row, col+1);
        helper(grid, row-1, col);