打印一个字符串的所有子序列
给定一个字符串，我们必须找出它的所有子序列。字符串是给定字符串的子序列，它是通过删除给定字符串的某些字符而不改变其顺序来生成的。
示例:
Input : abc
Output : a, b, c, ab, bc, ac, abc
Input : aaa
Output : a, aa, aaa
方法 1(挑与不挑概念)
c++
// C++ program for the above approach
#include <bits/stdc++.h>
using namespace std;
// Find all subsequences
void printSubsequence(string input, string output)
{
// Base Case
// if the input is empty print the output string
if (input.empty()) {
cout << output << endl;
return;
}
// output is passed with including
// the Ist character of
// Input string
printSubsequence(input.substr(1), output + input[0]);
// output is passed without
// including the Ist character
// of Input string
printSubsequence(input.substr(1), output);
}
// Driver code
int main()
{
// output is set to null before passing in as a
// parameter
string output = "";
string input = "abcd";
printSubsequence(input, output);
return 0;
}
Java
// Java program for the above approach
import java.util.*;
class GFG {
// Declare a global list
static List<String> al = new ArrayList<>();
// Creating a public static Arraylist such that
// we can store values
// IF there is any question of returning the
// we can directly return too// public static
// ArrayList<String> al = new ArrayList<String>();
public static void main(String[] args)
{
String s = "abcd";
findsubsequences(s, ""); // Calling a function
System.out.println(al);
}
private static void findsubsequences(String s,
String ans)
{
if (s.length() == 0) {
al.add(ans);
return;
}
// We add adding 1st character in string
findsubsequences(s.substring(1), ans + s.charAt(0));
// Not adding first character of the string
// because the concept of subsequence either
// character will present or not
findsubsequences(s.substring(1), ans);
}
}
python 3
# Below is the implementation of the above approach
def printSubsequence(input, output):
# Base Case
# if the input is empty print the output string
if len(input) == 0:
print(output, end=' ')
return
# output is passed with including the
# 1st character of input string
printSubsequence(input[1:], output+input[0])
# output is passed without including the
# 1st character of input string
printSubsequence(input[1:], output)
# Driver code
# output is set to null before passing in
# as a parameter
output = ""
input = "abcd"
printSubsequence(input, output)
# This code is contributed by Tharun Reddy
c
// C# program for the above approach
using System;
using System.Collections.Generic;
class GFG{
static void printSubsequence(string input,
string output)
{
// Base Case
// If the input is empty print the output string
if (input.Length == 0)
{
Console.WriteLine(output);
return;
}
// Output is passed with including
// the Ist character of
// Input string
printSubsequence(input.Substring(1),
output + input[0]);
// Output is passed without
// including the Ist character
// of Input string
printSubsequence(input.Substring(1),
output);
}
// Driver code
static void Main()
{
// output is set to null before passing
// in as a parameter
string output = "";
string input = "abcd";
printSubsequence(input, output);
}
}
// This code is contributed by SoumikMondal
Javascript
<script>
// JavaScript program for the above approach
// Find all subsequences
function printSubsequence(input, output)
{
// Base Case
// if the input is empty print the output string
if (input.length==0) {
document.write( output + "<br>");
return;
}
// output is passed with including
// the Ist character of
// Input string
printSubsequence(input.substring(1), output + input[0]);
// output is passed without
// including the Ist character
// of Input string
printSubsequence(input.substring(1), output);
}
// Driver code
// output is set to null before passing in as a
// parameter
var output = "";
var input = "abcd";
printSubsequence(input, output);
</script>
输出
abcd
abc
abd
ab
acd
ac
ad
a
bcd
bc
bd
b
cd
c
d
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