给定一个字符串数组，请按字母(字典)顺序打印它们。如果输入数组中有重复项，我们需要打印所有出现的情况。
例子：
Input : arr[] = { "abc", "xyz", "abcd", "bcd", "abc" }
Output : abc abc abcd bcd xyz
Input : arr[] = { "geeks", "for", "geeks", "a", "portal",
"to", "learn" }
Output : a for geeks geeks learn portal to先决条件： Trie | (插入和搜索)。
方法：在对上一个字符串数组进行排序时，仅打印一次出现的重复字符串。在这篇文章中，所有重复的字符串都按字典顺序打印。要按字母顺序打印字符串，我们必须先将它们插入到trie中，然后执行预遍历以按字母顺序打印。特里的节点包含一个index []数组，该数组存储以该节点结尾的所有arr []字符串的索引位置。除trie的叶节点外，其他所有节点的index []数组大小均为0。
下面是上述方法的实现。
C++
// C++ implementation to sort an array
// of strings using Trie
#include
using namespace std;
const int MAX_CHAR = 26;
struct Trie {
// 'index' vectors size is greater than
// 0 when node/ is a leaf node, otherwise
// size is 0;
vector index;
Trie* child[MAX_CHAR];
/*to make new trie*/
Trie()
{
// initializing fields
for (int i = 0; i < MAX_CHAR; i++)
child[i] = NULL;
}
};
// function to insert a string in trie
void insert(Trie* root, string str, int index)
{
Trie* node = root;
for (int i = 0; i < str.size(); i++) {
// taking ascii value to find index of
// child node
char ind = str[i] - 'a';
// making a new path if not already
if (!node->child[ind])
node->child[ind] = new Trie();
// go to next node
node = node->child[ind];
}
// Mark leaf (end of string) and store
// index of 'str' in index[]
(node->index).push_back(index);
}
// function for preorder traversal of trie
void preorder(Trie* node, string arr[])
{
// if node is empty
if (node == NULL)
return;
for (int i = 0; i < MAX_CHAR; i++) {
if (node->child[i] != NULL) {
// if leaf node then print all the strings
// for (node->child[i]->index).size() > 0)
for (int j = 0; j < (node->child[i]->index).size(); j++)
cout << arr[node->child[i]->index[j]] << " ";
preorder(node->child[i], arr);
}
}
}
// function to sort an array
// of strings using Trie
void printSorted(string arr[], int n)
{
Trie* root = new Trie();
// insert all strings of dictionary into trie
for (int i = 0; i < n; i++)
insert(root, arr[i], i);
// print strings in lexicographic order
preorder(root, arr);
}
// Driver program to test above
int main()
{
string arr[] = { "abc", "xyz", "abcd", "bcd", "abc" };
int n = sizeof(arr) / sizeof(arr[0]);
printSorted(arr, n);
return 0;
} Java
// Java implementation
// to sort an array of
// strings using Trie
import java.util.*;
class Trie {
private Node rootNode;
/*to make new trie*/
Trie()
{
rootNode = null;
}
// function to insert
// a string in trie
void insert(String key, int index)
{
// making a new path
// if not already
if (rootNode == null)
{
rootNode = new Node();
}
Node currentNode = rootNode;
for (int i = 0;i < key.length();i++)
{
char keyChar = key.charAt(i);
if (currentNode.getChild(keyChar) == null)
{
currentNode.addChild(keyChar);
}
// go to next node
currentNode = currentNode.getChild(keyChar);
}
// Mark leaf (end of string)
// and store index of 'str'
// in index[]
currentNode.addIndex(index);
}
void traversePreorder(String[] array)
{
traversePreorder(rootNode, array);
}
// function for preorder
// traversal of trie
private void traversePreorder(Node node,
String[] array)
{
if (node == null)
{
return;
}
if (node.getIndices().size() > 0)
{
for (int index : node.getIndices())
{
System.out.print(array[index] + " ");
}
}
for (char index = 'a';index <= 'z';index++)
{
traversePreorder(node.getChild(index), array);
}
}
private static class Node {
private Node[] children;
private List indices;
Node()
{
children = new Node[26];
indices = new ArrayList<>(0);
}
Node getChild(char index)
{
if (index < 'a' || index > 'z')
{
return null;
}
return children[index - 'a'];
}
void addChild(char index)
{
if (index < 'a' || index > 'z')
{
return;
}
Node node = new Node();
children[index - 'a'] = node;
}
List getIndices()
{
return indices;
}
void addIndex(int index)
{
indices.add(index);
}
}
}
class SortStrings {
// Driver program
public static void main(String[] args)
{
String[] array = { "abc", "xyz",
"abcd", "bcd", "abc" };
printInSortedOrder(array);
}
// function to sort an array
// of strings using Trie
private static void printInSortedOrder(String[] array)
{
Trie trie = new Trie();
for (int i = 0;i < array.length;i++)
{
trie.insert(array[i], i);
}
trie.traversePreorder(array);
}
}
// Contributed by Harikrishnan Rajan C#
// C# implementation
// to sort an array of
// strings using Trie
using System;
using System.Collections.Generic;
public class Trie
{
public Node rootNode;
/* to make new trie*/
public Trie()
{
rootNode = null;
}
// function to insert
// a string in trie
public void insert(String key, int index)
{
// making a new path
// if not already
if (rootNode == null)
{
rootNode = new Node();
}
Node currentNode = rootNode;
for (int i = 0;i < key.Length;i++)
{
char keyChar = key[i];
if (currentNode.getChild(keyChar) == null)
{
currentNode.addChild(keyChar);
}
// go to next node
currentNode = currentNode.getChild(keyChar);
}
// Mark leaf (end of string)
// and store index of 'str'
// in index[]
currentNode.addIndex(index);
}
public void traversePreorder(String[] array)
{
traversePreorder(rootNode, array);
}
// function for preorder
// traversal of trie
public void traversePreorder(Node node,
String[] array)
{
if (node == null)
{
return;
}
if (node.getIndices().Count > 0)
{
foreach (int index in node.getIndices())
{
Console.Write(array[index] + " ");
}
}
for (char index = 'a';index <= 'z';index++)
{
traversePreorder(node.getChild(index), array);
}
}
public class Node
{
public Node[] children;
public List indices;
public Node()
{
children = new Node[26];
indices = new List(0);
}
public Node getChild(char index)
{
if (index < 'a' || index > 'z')
{
return null;
}
return children[index - 'a'];
}
public void addChild(char index)
{
if (index < 'a' || index > 'z')
{
return;
}
Node node = new Node();
children[index - 'a'] = node;
}
public List getIndices()
{
return indices;
}
public void addIndex(int index)
{
indices.Add(index);
}
}
}
public class SortStrings
{
// Driver code
public static void Main(String[] args)
{
String[] array = { "abc", "xyz",
"abcd", "bcd", "abc" };
printInSortedOrder(array);
}
// function to sort an array
// of strings using Trie
static void printInSortedOrder(String[] array)
{
Trie trie = new Trie();
for (int i = 0;i < array.Length;i++)
{
trie.insert(array[i], i);
}
trie.traversePreorder(array);
}
}
// This code has been contributed by 29AjayKumar Python3
# Python implementation to sort an array
# of strings using Trie
from typing import List
MAX_CHAR = 26
class Trie:
def __init__(self) -> None:
# 'index' vectors size is greater than
# 0 when node/ is a leaf node, otherwise
# size is 0;
self.index = []
self.child = [None for _ in range(MAX_CHAR)]
# function to insert a string in trie
def insert(root: Trie, string: str, index: int) -> None:
node = root
for i in range(len(string)):
# taking ascii value to find index of
# child node
ind = ord(string[i]) - ord('a')
# making a new path if not already
if (node.child[ind] == None):
node.child[ind] = Trie()
# go to next node
node = node.child[ind]
# Mark leaf (end of string) and store
# index of 'str' in index[]
(node.index).append(index)
# function for preorder traversal of trie
def preorder(node: Trie, arr: List[str]) -> None:
# if node is empty
if (node == None):
return
for i in range(MAX_CHAR):
if (node.child[i] != None):
# if leaf node then print all the strings
# for (node.child[i].index).size() > 0)
for j in range(len(node.child[i].index)):
print(arr[node.child[i].index[j]], end = " ")
preorder(node.child[i], arr)
# function to sort an array
# of strings using Trie
def printSorted(arr: List[str], n: int) -> None:
root = Trie()
# insert all strings of dictionary into trie
for i in range(n):
insert(root, arr[i], i)
# print strings in lexicographic order
preorder(root, arr)
# Driver program to test above
if __name__ == "__main__":
arr = ["abc", "xyz", "abcd", "bcd", "abc"]
n = len(arr)
printSorted(arr, n)
# This code is contributed by sanjeev2552输出：
abc abc abcd bcd xyz时间复杂度：最坏的情况是每个字符串都以不同的字符开头时。在这种情况下，它将访问每个字符串的每个字符的所有节点。因此，最坏情况下的时间复杂度将是每个字符串的长度之和，即O(| S1 | + | S2 | + | S3 | +…+ | Sn |)其中| S |是字符串的长度。