leetcode之Bulls and Cows

题目：

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.

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 should return "1A3B".

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 1 in friend's guess is a bull, the 2nd or 3rd 1 is a cow, and your function should return "1A1B".

You may assume that the secret number and your friend's guess only contain digits, and their lengths are always equal.

解答：

先扫描一遍,将已经配对的直接记录，标记未配对的，然后再扫面一遍看有多少B

从这道题目我也发现了自己一直一来过于依赖STL的毛病，很多时候同样的算法，由于map，vector的使用导致在时间上出现几十毫秒的差距。这道题一开始用map保存数据是32ms，后来改为直接用数据，时间下降到4ms

class Solution {public:    string getHint(string secret, string guess) {        int len = secret.length();        int record[10] = {0};        int cntA = 0;        int cntB = 0;        for(int i = 0;i < len;++i)        {            if(secret[i] == guess[i])            {                                cntA++;                guess[i] = ' ';            }            else            {                record[secret[i] - '0']++;            }        }        for(int i = 0;i < len;++i)        {            if(guess[i] == ' ')                continue;            else            {                if(record[guess[i] - '0'] > 0)                {                    cntB++;                    record[guess[i] - '0']--;                }            }        }        string res = to_string(cntA) + "A" + to_string(cntB) + "B";        return res;    }};