CF730H：Delete Them（字符串处理）

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解决一个编程问题，通过创建一个模式来精确匹配指定的文件列表并避免误删其他文件。任务涉及分析多个字符串，找出共同特征，并构建一个通用模式。

Polycarp is a beginner programmer. He is studying how to use a command line.

Polycarp faced the following problem. There are n files in a directory and he needs to delete some of them. Polycarp wants to run a single delete command with filename pattern as an argument. All the files to be deleted should match the pattern and all other files shouldn't match the pattern.

Polycarp doesn't know about an asterisk '*', the only special character he knows is a question mark '?' which matches any single character. All other characters in the pattern match themselves only.

Formally, a pattern matches a filename if and only if they have equal lengths and all characters in the corresponding positions are equal except when the character in the pattern is '?', in which case the corresponding filename character does not matter.

For example, the filename pattern "a?ba?":

matches filenames "aabaa", "abba.", "a.ba9" and "a.ba.";
does not match filenames "aaba", "abaab", "aabaaa" and "aabaa.".

Help Polycarp find a pattern which matches files to be deleted and only them or report if there is no such pattern.

Input

The first line of the input contains two integers n and m (1 ≤ m ≤ n ≤ 100) — the total number of files and the number of files to be deleted.

The following n lines contain filenames, single filename per line. All filenames are non-empty strings containing only lowercase English letters, digits and dots ('.'). The length of each filename doesn't exceed 100. It is guaranteed that all filenames are distinct.

The last line of the input contains m distinct integer numbers in ascending order a1, a2, ..., am (1 ≤ ai ≤ n) — indices of files to be deleted. All files are indexed from 1 to n in order of their appearance in the input.

Output

If the required pattern exists, print "Yes" in the first line of the output. The second line should contain the required pattern. If there are multiple solutions, print any of them.

If the required pattern doesn't exist, print the only line containing "No".

Examples

input
3 2
ab
ac
cd
1 2

output
Yes
a?

input
5 3
test
tezt
test.
.est
tes.
1 4 5

output
Yes
?es?

input
4 4
a
b
c
dd
1 2 3 4

output
No

input
6 3
.svn
.git
....
...
..
.
1 2 3

output
Yes
.???

题意：给N个字符串，要指定删除其中的M条，要求输出一条匹配字符串：将这M条字串的公有字符保留，其余换成'?'，且该匹配字符不能误杀其他不能删除的字符串。若不存在这样的匹配字符串输出No。

# include <stdio.h>
# include <string.h>
char a[102][101];
int b[101], slen[101];
int main()
{
    int n, m;
    while(~scanf("%d%d",&n,&m))
    {
        memset(a[101], 0, sizeof(a[101]));
        int len = 0, flag = 0, num=0, val=0;
        for(int i=1; i<=n; ++i)
        {
            scanf("%s",a[i]);
            slen[i] = strlen(a[i]);
        }
        for(int i=0; i<m; ++i)
        {
            scanf("%d",&b[i]);
            if(flag)
                continue;
            if(!len)
                len = slen[b[i]];
            else
                flag = (len != slen[b[i]]);//判断这M条字符串长度是否相等。
        }
        if(flag)
        {
            puts("No");
            continue;
        }
        for(int i=0; i<len; ++i)
        {
            char c = a[b[0]][i];
            int flag2 = 0;
            for(int j=1; j<m; ++j)
                if(a[b[j]][i] != c)
                {
                    ++num;
                    flag2 = 1;
                    break;
                }
            a[101][i] = flag2?'?':c;
        }
        val = len - num;//记录非'?'的字符个数。
        num = 0;
        for(int i=1; i<=n; ++i)//判断会不会误杀其他字符串。
            if(slen[i] == len)
            {
                int tmp = 0;
                for(int j=0; j<len; ++j)
                    if(a[101][j] != '?' && a[101][j] == a[i][j])
                        ++tmp;
                if(tmp == val)
                    ++num;
            }
        if(num > m)
        {
            puts("No");
            continue;
        }
        printf("Yes\n%s\n",a[101]);
    }
    return 0;
}