LeetCode -- Bulls and Cows

LeetCode -- Bulls and Cows
Description:


You are playing the following Bulls and Cows game with your friend: You write down a number and ask your friend to guess what the number is. each time your friend makes a guess, you provide a hint that indicates how many digits in said guess match your secret number exactly in both digit and position (called bulls) and how to adjust digits match the secret number but locate in the wrong position (called cows ). your friend will use successive guesses and hints to eventually derive the secret number.


For example:


Secret number: 1807
Friend's guess: 7810
Hint: 1 bull and 3 cows. (The bull is 8, the cows are 0, 1 and 7 .)
Write a function to return a hint according to the secret number and friend's guess, use A to indicate the bulls and B to indicate the cows. in the above example, your function shocould return 1A3B.


Please note that both secret number and friend's guess may contain in duplicate digits, for example:


Secret number: 1123
Friend's guess: 0111
In this case, the 1st 1 in friend's guess is a bull, the 2nd or 3rd 1 is a cow, and your function shocould return 1A1B.
You may assume that the secret number and your friend's guess only contain digits, and their lengths are always equal.


Returns the string s, which contains a number ranging from 0 to 9. If a string t is input, it is required to judge whether every bit of t [j] And s [j] (j, [0, N) is equal. If they are equal, it is regarded as Bulls; if not, check whether t [j] is equal to s [I], where I! = J. If yes, it is regarded as cows.


1. In this question, we can use a hash table to compare each digit of guess and secret over the first calendar to obtain the number of bulls. At the same time, the number of occurrences of each bit of s [I] is counted and saved to the hash table hash.
2. If bulls is equal to the length of s, it indicates that secret and guess match completely. Return bulls directly.
3. traverse every bit of guess. If guess appears in hash and hash [guess [I] is greater than 0, hash [guess [I] -- and count the number of cows.
4. Finally, return the number of bulls and cows.




Implementation Code:

public class Solution {    public string GetHint(string secret, string guess)     {        var bulls = 0;    var hash = new Dictionary
 
  ();    for(var i = 0;i < secret.Length; i++){    if(guess[i] == secret[i]){    bulls++;    }    if(!hash.ContainsKey(secret[i])){    hash.Add(secret[i], 1);    }    else{    hash[secret[i]]++;    }    }        if(bulls == secret.Length){    return string.Format({0}A0B,bulls);    }        var guessed = 0;    for(var i = 0;i < guess.Length; i++){    if(hash.ContainsKey(guess[i]) && hash[guess[i]] > 0){    hash[guess[i]] --;    guessed ++;    }    }        guessed -= bulls;        return string.Format({0}A{1}B, bulls , guessed);    }}