Crack Leetcode 1

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Hello world! I try to write down every progress I’ve made from now on. Start with Leetcode. By acceptance order, I will provide my thinking and answer.

#771 Jewels and Stones（C++ version）

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class Solution {
public:
    int numJewelsInStones(string J, string S) {
        int count=0;
        for(int i=0;i<J.size();i++){
            for(int j=0;j<S.size();j++){
                if(J[i]==S[j]){
                    count++;
                }
            }
        }
        return count;
    }
};

#938 Range Sum of BST （C++ version）

I used recursion method

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class Solution {
public:
    int rangeSumBST(TreeNode* root, int L, int R) {
        int count = 0;
         if(root==NULL)
            return 0;
        if(root->val >= L && root->val <=R)
            count += root->val;
        if(root->val >= L){
            count += rangeSumBST(root->left,L,R);
        }
        if(root->val <= R){
            count += rangeSumBST(root->right,L,R);
        }
       
        return count;
    }
};

#807 Max Increase to Keep City Skyline(C++)

What I think is for every grid, the value equals min(the max value in the column,the max value in that line)

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class Solution {
public:
    int maxIncreaseKeepingSkyline(vector<vector<int>>& grid) {
        vector<int> grid_top;
        vector<int> grid_left;
        int count = 0;
        for(int i=0;i<grid[0].size();i++){
            grid_left.push_back(findMax(grid[i]));
            int max = grid[0][i];
            for(int j=0;j<grid.size();j++){
                if(grid[j][i] >= max)
                    max = grid[j][i];
            }
            grid_top.push_back(max);
        }
      
        for(int i=0;i<grid.size();i++){
            for(int j=0;j<grid[0].size();j++){
                int temp = min(grid_left[j],grid_top[i]);
                count += temp - grid[i][j];
            }
        }
        return count;
    }
    int findMax(vector<int> list){
        int max = list[0];
        for(int i=1;i<list.size();i++){
            if(list[i] >= max)
                max = list[i];
        }
        return max;
    }
};

#929 Unique Email Addresses(C++ version)

I realized the split function is reeeealy useful, maybe it’s time to switch to Java or Python :D

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class Solution {
public:
    int numUniqueEmails(vector<string>& emails) {
        vector<string> newEmails;
        for(int i=0;i<emails.size();i++){
            string email = emails[i];
            string email_temp;
            int plus_flag = 0;
            int at_flag = 0;
            for(int j=0;j<email.length();j++){
                if(email[j] == '+')
                    plus_flag = 1;
                
                if(!plus_flag){
                    if(email[j] != '.'){
                        email_temp = email_temp + email[j];
                    }
                }
                if(email[j] == '@'){
                    at_flag = 1;
                }
                if(at_flag){
                    email_temp= email_temp + email[j];
                }   
            }
            int same = 0;
            for(int i=0;i<newEmails.size();i++){
                if(newEmails[i] == email_temp)
                    same = 1;
            }
            if(!same)
                newEmails.push_back(email_temp);
           
        }
        return newEmails.size();
    }
};

#709. To Lower Case(Yes Java version)

It is about Ascii

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class Solution {
    public String toLowerCase(String str) {
        String result = "";
        for(int i=0;i<str.length();i++){
            int temp = str.charAt(i);
            int ascii = temp;
            if(temp <= 90 &&temp >= 65){
            	char r= (char) (temp + 32);
                result += r;
            }else{
                result += str.charAt(i);
            }
        }
        return result;
    }
}

#804 Unique Morse Code Words

First find the morse code for each word, then duplicate checking

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class Solution {
    public int uniqueMorseRepresentations(String[] words) {
        String[] secrets = {".-","-...","-.-.","-..",".","..-.","--.","....","..",".---","-.-",".-..","--","-.","---",".--.","--.-",".-.","...","-","..-","...-",".--","-..-","-.--","--.."};
        Set<String> set = new HashSet<String>();
        for(String word:words){
        	String secretWord = "";
        	for(int i=0;i<word.length();i++) {
        		secretWord += secrets[(int)word.charAt(i)-97];
        	}
        	set.add(secretWord);
        }
        return set.size();
    }
}