leetcode Bulls and Cows
You are playing the following Bulls and Cows game with your friend: You write a 4-digit secret number and ask your friend to guess it. Each time your friend guesses a number, you give a hint. The hint tells your friend how many digits are in the correct positions (called "bulls") and how many digits are in the wrong positions (called "cows"). Your friend will use those hints to find out the secret number.
- Secret number: "1807"
- Friend's guess: "7810"
3cows. (The bull is
8, the cows are
Write a function to return a hint according to the secret number and friend's guess, use
Ato indicate the bulls and
Bto indicate the cows. In the above example, your function should return
Please note that both secret number and friend's guess may contain duplicate digits, for example:
- Secret number: "1123"
- Friend's guess: "0111"
In this case, the 1st
1in friend's guess is a bull, the 2nd or 3rd
1is a cow, and your function should return
You may assume that the secret number and your friend's guess only contain digits, and their lengths are always equal. 题目地址：leetcode Bulls and Cows