walkingtospace

https://leetcode.com/problems/number-of-1-bits/

class Solution {
public:
    int hammingWeight(uint32_t n) {
        int size = 32; //uint32
        int numOne = 1;
        int cnt = 0;
        
        for(int i=0; i<size ; ++i) {

walkingtospace

https://leetcode.com/problems/excel-sheet-column-number/

//Key point: this problem is just 26th-decimal transformation.

//input : only capital? no exception?
//O(l); l is the length of the given input

//test case
//A, Z, AA, BB, AAA

walkingtospace

#include <stdio.h>
#include <time.h>

typedef struct {
	union {
		char * company;
		char * school;
		char * project;
	};
	union {

walkingtospace

https://oj.leetcode.com/problems/search-a-2d-matrix/

/*
I think the the most important hint is the fact that this matrix is already sorted.
just think of the binary search.
I could know the length of each row, thus start from the first element of the middle row(2/n), compare then move to 4/n ... 

test case1
long column: [1,2,3,4,5,6,7,8,9,10,11,12...]

walkingtospace

https://oj.leetcode.com/problems/permutations/

class Solution {
public:
    vector<vector<int>> permute(vector<int> &num) {
        vector<vector<int>> res;
        
        if(num.size() == 0) {
            return res;
        }

walkingtospace

https://oj.leetcode.com/problems/permutations/
class Solution {
public:
    vector<vector<int>> permute(vector<int> &num) {
        vector<vector<int>> res;
        
        if(num.size() == 0) {
            return res;
        }
        

walkingtospace

https://oj.leetcode.com/problems/binary-tree-level-order-traversal-ii/

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

walkingtospace

https://oj.leetcode.com/problems/unique-paths/

/*
let's count the number of cases:
m,n=00/10/01 .. 1
m,n=1,1 1
m,n=1,2 1
m,n=1,3 1
m,n=2,1 1
m,n=2,2 (2,1) + (1,2) = 2

walkingtospace

https://oj.leetcode.com/problems/generate-parentheses/

/*
"well-formed" 의미를 시작전 명확하게 인터뷰어와 논의. 여기서는 열고( 닫는) 한쌍의 괄호쌍 의미
좀 더 정확하게 정의해보면, 닫힌 괄호가 나왔을때, 앞에 매칭되는 열린괄호가 최소한 1개는 존재해야함. 

n=1 (), 
n=2 (()), ()()
n=3 ()(()), (()()), ((())), (()()), (())(), ()()()
n=4 ..

walkingtospace

https://oj.leetcode.com/problems/rotate-image/

/*
tese case

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