Array - 299. Bulls and Cows

299、Bulls and Cows

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 many 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.

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. 

Please note that both secret number and friend's guess may contain duplicate digits.

Example 1:

Input: secret = "1807", guess = "7810"

Output: "1A3B"

Explanation: 1 bull and 3 cows. The bull is 8, the cows are 0, 1 and 7.

思路：

公母牛这题因为是猜数字，所以可以使用一个数组，存储每一个字节对应的数字。 这样就可以用一个大小为10的数组来存储secret字串和guess字串中出现的char，使用一次遍历就可以得到结果。

代码：

go：

func getHint(secret string, guess string) string {

    if secret == "" || len(secret) == 0 {return "0A0B"}
    
    maps := make([]int, 10)
    bull, cow := 0, 0
    
    for i, v := range secret {
        s := int(v - '0')
        g := int(guess[i] - '0')
        if s == g {
            bull++
        } else {
            if maps[g]>0 {cow++}
            if maps[s]<0 {cow++}
            maps[g]--
            maps[s]++
        }
    }
    
    return strconv.Itoa(bull) + "A" + strconv.Itoa(cow) + "B"
}