随机抽样长度为k的非重叠子串

Question

给定一个长度为n的字符串,我将如何(伪)随机采样大小为k的m个子串,使得所有采样的子串都不重叠？我的大部分脚本编写经验都在Perl中,但是使用任何通用语言的易于运行的解决方案就足够了.

Answer 1

如果输入中存在不能出现的字符，例如X，则：

my $size = 20;
my $count = 20;
my $mark = 'X';
my $input = 'CCACGCATTTTTGTTCATTGTTCTGGCTTCTTACAAGGTTCAGTAGACTTTGTAACACAGTTGTGTCTCTCACAGATTGGCAGATGTTTGGTAAAGGATTGACTTTTCAGCCAACTCATGGGAAAGTGAAATAATGTAAAAAACAGGAAGAATACAGTTTTAGGCCTTTCAAGTGAGGCATGGCTTTCAGCTCTTGGCAAGAACAGGCAAGGAGATGCAAGTTTTAGGACTCTAAGAGGCTAGGCTTTTCAAAGTGCTTCTCTCCCCTTCACCCTCCTTCAGTTACAGCACCAAGCACCACCGAGGTGTTACCTGCAGCCTCACTCTCTACCTGGTTGTGGGATCCTGCCACTTCCTTAACCCACACTGAGTTCCTTGTGGTTCACAGGGTCACACAGAGGGCTGTAGAGATACAAAAGATATATGTGATTTTATATCACCTATCATATGAAGATATATTTATAAAATAGGAAACATATTAACCACTTATCATTTTATATATTTATGGTTTTATGTGTCAAAAATATATTGTTTCATGTATGTATTAAAGGATAAGTATGTATAAGAGGTTTTATAGATGTGTAAAATTATATATTTATACGTATCTTTACAAATTTAAGAATAAAGGAAGGAAAATTCTCAAAGAGGAATTCAGATATCAAGCAGTGCCCTTTGACCAAGAGCCTTGGTTACAACATACCTACAAAAGTGAACTATCATTGAAAGACCTATGGACACTGGATTTCTCTTTCCTTATTTAGAAGGGCAGTCTGTGTCTTGGAAAAGCATACAGTTTGTTGTATCTTGCTGGACAACAGGAGTCA';

if (2*$size*$count-$size-$count >= length($input)) {
    die "selection may not complete; choose a shorter length or fewer substrings, or provide a longer input string\n";
}

my @substrings;
while (@substrings < $count) {
    my $pos = int rand(length($input)-$size+1);
    push @substrings, substr($input, $pos, $size, $mark x $size)
        if substr($input, $pos, $size) !~ /\Q$mark/;
}