s4553711

class Solution {
public:
    bool validPalindrome(string s) {
        return valid(s, 0, s.length() - 1, 1);
    }
    bool valid(string& s, int i, int j, int d) {
        if (i >= j) return true;
        if (s[i] == s[j]) 
            return valid(s, i + 1, j - 1, d);
        else

s4553711

class Solution {
public:
    bool checkPerfectNumber(int num) {
        int result = 1;
        for(int i = 2; i < sqrt(num); i++) {
            if (num%i == 0) {
                //cout << result << ", " << i << endl;
                result += i + num/i;
            }
        }

s4553711

class Solution {
public:
    bool wordPattern(string pattern, string str) {
        str += ' ';
        int i = 0, j = 0, len1 = pattern.size(), len2 = str.size();
        unordered_map<char, string> hash1;
        unordered_map<string, char> hash2;
        while(i < len1 && j < len2) {
            int pos = str.find(' ', j);
            string s = str.substr(j, pos-j);

s4553711

/**
 * 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 {

s4553711

class Solution {
public:
    bool canConstruct(string ransomNote, string magazine) {
        unordered_map<char, int> res(26);
        for(int i = 0; i < magazine.size(); i++)
            ++res[magazine[i]];
        for(int j = 0; j < ransomNote.size(); j++)
            if (--res[ransomNote[j]] < 0) return false;
        return true;
    }

s4553711

class Solution {
public:
    int calculate(string s) {
        s += "+";
        stack<int> st;
        char old = '+';
        for(int i = 0, left = 0; i < s.size(); i++) {
            if (isdigit(s[i]) || isspace(s[i])) continue;
            int val = stoi(s.substr(left, i-left));
            if (old == '+' || old == '-') st.push(old == '+' ? val : -val);

s4553711

class Solution {
public:
    bool isToeplitzMatrix(vector<vector<int>>& matrix) {
        for(int i = 1; i < matrix.size(); i++) {
            for(int j = 1; j < matrix[i].size(); j++) {
                if (matrix[i][j] != matrix[i-1][j-1]) return false;
            }
        }
        return true;
    }

s4553711

class Solution {
public:
    void rotate(vector<vector<int>>& matrix) {
        int n = matrix.size();
        for(int i = 0; i < n; i++) {
            for(int j = 0; j < i; j++)
                swap(matrix[i][j], matrix[j][i]);
        }
        
        for(int i = 0; i < n; i++)

s4553711

class Solution {
public:
    vector<int> selfDividingNumbers(int left, int right) {
        vector<int> res;
        for(int i = left; i <= right; i++) {
            int t = i;
            bool val = true;
            while(t && val) {
                const int r = t % 10;
                //cout << "r: " << r << ", i:" << i << ", i%r" << i%r << endl;

s4553711

class Solution {
public:
    int dominantIndex(vector<int>& nums) {
        int maxi = -1, seci = -1;
        for(int i = 0; i < nums.size(); i++) {
            // cout << "b: i: " << i << " m: " << maxi << ", s: " << seci << endl;
            if (nums[i] > nums[maxi]) {
                int tmp = maxi;
                maxi = i;
                seci = tmp;