给定数字字符串str ,其中1代表‘a’ ,2代表‘b’ ,…,26代表‘z’ ,任务是打印所有可以从str获得的字母字符串。
例子:
Input: str = “1123”
Output:
aabc
kbc
alc
aaw
kw
Explanation:
The given string can be splitted as:
1) “1123” = “1” + “1” + “2” + “3” = aabc
2) “1123” = “11” + “2” + “3” = kbc
3) “1123” = “1” + “12” + “3” = alc
4) “1123” = “1” + “1” + “23” = aaw
5) “1123” = “11” + “23” = aabc
Input: str = “56”
Output:
ef
Explanation:
The given string can be splitted as:
1) “56” = “5” + “6” = ef
方法:可以观察到,每个单个字符代表一个除0之外的字母。此问题是递归的,可以分解为子问题。终止条件为传递的字符串为空时。以下是解决问题的步骤:
- 创建一个辅助函数getChar() ,该函数返回给定数字字符的相应字母。
- 创建一个递归函数,该函数将输入作为字符串,并返回提取的每个字符的所需答案的数组。
- 基本情况是输入字符串为空时。在这种情况下,返回一个长度为1的数组,其中包含一个空字符串。
- 使用helper函数提取每个单个字符,然后将其附加到空字符串,然后将其存储在一个数组中,例如output1 。
- 同时检查字符长度是否大于或等于两个,还检查提取的两个字符是否在字母范围内。现在,将相应的字符存储在一个数组中,例如output2 。
- 然后创建一个最终的输出数组,其长度将是output1和output2的长度之和,并存储它们的答案并返回它。
- 对提取的每一个或一对相邻字符重复上述步骤。现在,返回获得的最终数组。
- 遍历数组并为每个字符串生成对应的小写字母字符串并打印出来。
下面是上述方法的实现:
C++
// C++ program for the above approach
#include
using namespace std;
// Function to check if all the
// characters are lowercase or not
bool nonLower(string s)
{
// Traverse the string
for(int i = 0; i < s.size(); i++)
{
// If any character is not
// found to be in lowerCase
if (!islower(s[i]))
{
return true;
}
}
return false;
}
// Function to print the decodings
void printCodes(vector output)
{
for(int i = 0; i < output.size(); i++)
{
// If all characters are not
// in lowercase
if (nonLower(output[i]))
continue;
cout << (output[i]) << endl;
}
}
// Fuction to return the character
// corresponding to given integer
char getChar(int n)
{
return (char)(n + 96);
}
// Function to return the decodings
vector getCode(string str)
{
// Base case
if (str.size() == 0)
{
vector ans;
ans.push_back("");
return ans;
}
// Recursive call
vector output1 = getCode(str.substr(1));
// Stores the characters of
// two digit numbers
vector output2(0);
// Extract first digit and
// first two digits
int firstDigit= (str[0] - '0');
int firstTwoDigit = 0;
if (str.size() >= 2)
{
firstTwoDigit = (str[0] - '0') * 10 +
(str[1] - '0');
// Check if it lies in the
// range of alphabets
if (firstTwoDigit >= 10 &&
firstTwoDigit <= 26)
{
// Next recursive call
output2 = getCode(str.substr(2));
}
}
// Combine both the output in a
// single final output array
vector output(output1.size() +
output2.size());
// Index of final output array
int k = 0;
// Store the elements of output1
// in final output array
for(int i = 0; i < output1.size(); i++)
{
char ch = getChar(firstDigit);
output[i] = ch + output1[i];
k++;
}
// Store the elements of output2
// in final output array
for(int i = 0; i < output2.size(); i++)
{
char ch = getChar(firstTwoDigit);
output[k] = ch + output2[i];
k++;
}
// Result the result
return output;
}
// Driver Code
int main()
{
string input = "101";
// Function call
vector output = getCode(input);
// Print function call
printCodes(output);
}
// This code is contributed by grand_master
Java
// Java program for the above approach
import java.io.*;
class GFG {
// Function to check if all the
// characters are lowercase or not
public static boolean
nonLower(String s)
{
// Traverse the string
for (int i = 0; i < s.length(); i++) {
// If any character is not
// found to be in lowerCase
if (!Character
.isLowerCase(s.charAt(i))) {
return true;
}
}
return false;
}
// Function to print the decodings
public static void
printCodes(String output[])
{
for (int i = 0; i < output.length; i++) {
// If all characters are not
// in lowercase
if (nonLower(output[i]))
continue;
System.out.println(output[i]);
}
}
// Fuction to return the character
// corresponding to given integer
public static char getChar(int n)
{
return (char)(n + 96);
}
// Function to return the decodings
public static String[] getCode(
String str)
{
// Base case
if (str.length() == 0) {
String ans[] = { "" };
return ans;
}
// Recursive call
String output1[]
= getCode(str.substring(1));
// Stores the characters of
// two digit numbers
String output2[] = new String[0];
// Extract first digit and
// first two digits
int firstDigit
= (str.charAt(0) - '0');
int firstTwoDigit = 0;
if (str.length() >= 2) {
firstTwoDigit
= (str.charAt(0) - '0') * 10
+ (str.charAt(1) - '0');
// Check if it lies in the
// range of alphabets
if (firstTwoDigit >= 10
&& firstTwoDigit <= 26) {
// Next recursive call
output2
= getCode(str.substring(2));
}
}
// Combine both the output in a
// single final output array
String output[]
= new String[output1.length
+ output2.length];
// Index of final output array
int k = 0;
// Store the elements of output1
// in final output array
for (int i = 0; i < output1.length; i++) {
char ch = getChar(firstDigit);
output[i] = ch + output1[i];
k++;
}
// Store the elements of output2
// in final output array
for (int i = 0; i < output2.length; i++) {
char ch = getChar(firstTwoDigit);
output[k] = ch + output2[i];
k++;
}
// Result the result
return output;
}
// Driver Code
public static void main(String[] args)
{
String input = "101";
// Function call
String output[] = getCode(input);
// Print function call
printCodes(output);
}
}
Python3
# Python3 program for
# the above approach
# Function to check if all the
# characters are lowercase or not
def nonLower(s):
# Traverse the string
for i in range(len(s)):
# If any character is not
# found to be in lowerCase
if not s[i].islower():
return True
return False
# Function to print the decodings
def printCodes(output):
for i in range(len(output)):
# If all characters are not
# in lowercase
if (nonLower(output[i])):
continue
print(output[i])
# Fuction to return the character
# corresponding to given integer
def getChar(n):
return chr(n + 96)
# Function to return the decodings
def getCode(str):
# Base case
if (len(str) == 0):
ans = [""]
return ans
# Recursive call
output1 = getCode(str[1:])
# Stores the characters of
# two digit numbers
output2 = []
# Extract first digit and
# first two digits
firstDigit = (ord(str[0]) - ord('0'))
firstTwoDigit = 0
if (len(str) >= 2):
firstTwoDigit = ((ord(str[0]) - ord('0')) * 10 +
(ord(str[1]) - ord('0')))
# Check if it lies in the
# range of alphabets
if (firstTwoDigit >= 10 and firstTwoDigit <= 26):
# Next recursive call
output2 = getCode(str[2:])
# Combine both the output in a
# single readonly output array
output = ['' for i in range(len(output1) +
len(output2))]
# Index of readonly output array
k = 0
# Store the elements of output1
# in readonly output array
for i in range(len(output1)):
ch = getChar(firstDigit)
output[i] = ch + output1[i]
k += 1
# Store the elements of output2
# in readonly output array
for i in range(len(output2)):
ch = getChar(firstTwoDigit)
output[k] = ch + output2[i]
k += 1
# Result the result
return output
# Driver Code
if __name__=='__main__':
input = "101"
# Function call
output = getCode(input)
# Print function call
printCodes(output)
# This code is contributed by rutvik_56
C#
// C# program for
// the above approach
using System;
class GFG{
// Function to check if all the
// characters are lowercase or not
public static bool nonLower(String s)
{
// Traverse the string
for (int i = 0; i < s.Length; i++)
{
// If any character is not
// found to be in lowerCase
if (!char.IsLower(s[i]))
{
return true;
}
}
return false;
}
// Function to print the decodings
public static void printCodes(String []output)
{
for (int i = 0; i < output.Length; i++)
{
// If all characters are not
// in lowercase
if (nonLower(output[i]))
continue;
Console.WriteLine(output[i]);
}
}
// Fuction to return the character
// corresponding to given integer
public static char getChar(int n)
{
return (char)(n + 96);
}
// Function to return the decodings
public static String[] getCode(String str)
{
// Base case
if (str.Length == 0)
{
String []ans = { "" };
return ans;
}
// Recursive call
String []output1 = getCode(str.Substring(1));
// Stores the characters of
// two digit numbers
String []output2 = new String[0];
// Extract first digit and
// first two digits
int firstDigit = (str[0] - '0');
int firstTwoDigit = 0;
if (str.Length >= 2)
{
firstTwoDigit = (str[0] - '0') * 10 +
(str[1] - '0');
// Check if it lies in the
// range of alphabets
if (firstTwoDigit >= 10 &&
firstTwoDigit <= 26)
{
// Next recursive call
output2 = getCode(str.Substring(2));
}
}
// Combine both the output in a
// single readonly output array
String []output = new String[output1.Length +
output2.Length];
// Index of readonly output array
int k = 0;
// Store the elements of output1
// in readonly output array
for (int i = 0; i < output1.Length; i++)
{
char ch = getChar(firstDigit);
output[i] = ch + output1[i];
k++;
}
// Store the elements of output2
// in readonly output array
for (int i = 0; i < output2.Length; i++)
{
char ch = getChar(firstTwoDigit);
output[k] = ch + output2[i];
k++;
}
// Result the result
return output;
}
// Driver Code
public static void Main(String[] args)
{
String input = "101";
// Function call
String []output = getCode(input);
// Print function call
printCodes(output);
}
}
// This code is contributed by Rajput-Ji
输出:
ja
时间复杂度: O(2 N )
空间复杂度: O(N)