打印字符串的子序列

题目

打印一个字符串的全部子序列, 包括空字符串

题解

迭代过程中, 要么当前字符保留, 要么略过

Java

public class Subsequence {
    public static void printAllSub(String str) {
        char[] chs = str.toCharArray();
        process(chs, 0, "");
        System.out.println("");
    }

    public static void process(char[] chs, int i, String pre) {
        if (i == chs.length) {
            if (!pre.equals("")) {
                System.out.println(pre);
            }
            return;
        }
        process(chs, i + 1, pre + String.valueOf(chs[i]));
        process(chs, i + 1, pre);
    }

    public static void main(String[] args) {
        String test = "abc";
        printAllSub(test);
    }
}

abc
ab
ac
a
bc
b
c

Python

def print_subsequence(string):
    str_arr = [i for i in string]
    process(str_arr, 0, '')
    print()


def process(str_arr, i, pre):
    if i == len(str_arr):
        if pre != '':
            print(pre)
        return
    process(str_arr, i + 1, pre + str_arr[i])
    process(str_arr, i + 1, pre)