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Add multiple algorithms (#2442)

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RITWEEK RAJ
2021-10-03 15:13:03 +05:30
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commit 7cc96f9a15
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183
Others/Implementing_auto_completing_features_using_trie.java Normal file
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package Others;
// Java Program to implement Auto-Complete
// Feature using Trie
import java.util.*;
import java.io.*;
import java.lang.*;
class Trieac {
// Alphabet size (# of symbols)
public static final int ALPHABET_SIZE = 26;
// Trie node
static class TrieNode
{
TrieNode children[] = new TrieNode[ALPHABET_SIZE];
// isWordEnd is true if the node represents
// end of a word
boolean isWordEnd;
};
// Returns new trie node (initialized to NULLs)
static TrieNode getNode() {
TrieNode pNode = new TrieNode();
pNode.isWordEnd = false;
for(int i = 0; i < ALPHABET_SIZE; i++)
pNode.children[i] = null;
return pNode;
}
// If not present, inserts key into trie. If the
// key is prefix of trie node, just marks leaf node
static void insert(TrieNode root, final String key)
{
TrieNode pCrawl = root;
for(int level = 0; level < key.length(); level++)
{
int index = (key.charAt(level) - 'a');
if (pCrawl.children[index] == null)
pCrawl.children[index] = getNode();
pCrawl = pCrawl.children[index];
}
// mark last node as leaf
pCrawl.isWordEnd = true;
}
// Returns true if key presents in trie, else false
boolean search(TrieNode root, final String key)
{
int length = key.length();
TrieNode pCrawl = root;
for (int level = 0; level < length; level++)
{
int index = (key.charAt(level) - 'a');
if (pCrawl.children[index] == null)
pCrawl = pCrawl.children[index];
}
return (pCrawl != null && pCrawl.isWordEnd);
}
// Returns 0 if current node has a child
// If all children are NULL, return 1.
static boolean isLastNode(TrieNode root)
{
for (int i = 0; i < ALPHABET_SIZE; i++)
if (root.children[i] != null)
return false;
return true;
}
// Recursive function to print auto-suggestions
// for given node.
static void suggestionsRec(TrieNode root, String currPrefix)
{
// found a string in Trie with the given prefix
if (root.isWordEnd)
{
System.out.println(currPrefix);
}
// All children struct node pointers are NULL
if (isLastNode(root))
return;
for (int i = 0; i < ALPHABET_SIZE; i++)
{
if (root.children[i] != null)
{
// append current character to currPrefix string
currPrefix += (char)(97 + i);
// recur over the rest
suggestionsRec(root.children[i], currPrefix);
}
}
}
// Fucntion to print suggestions for
// given query prefix.
static int printAutoSuggestions(TrieNode root,
final String query)
{
TrieNode pCrawl = root;
// Check if prefix is present and find the
// the node (of last level) with last character
// of given string.
int level;
int n = query.length();
for (level = 0; level < n; level++)
{
int index = (query.charAt(level) - 'a');
// no string in the Trie has this prefix
if (pCrawl.children[index] == null)
return 0;
pCrawl = pCrawl.children[index];
}
// If prefix is present as a word.
boolean isWord = (pCrawl.isWordEnd == true);
// If prefix is last node of tree (has no
// children)
boolean isLast = isLastNode(pCrawl);
// If prefix is present as a word, but
// there is no subtree below the last
// matching node.
if (isWord && isLast)
{
System.out.println(query);
return -1;
}
// If there are are nodes below last
// matching character.
if (!isLast)
{
String prefix = query;
suggestionsRec(pCrawl, prefix);
return 1;
}
return 0;
}
// Driver code
public static void main(String[] args)
{
TrieNode root = getNode();
insert(root, "hello");
insert(root, "dog");
insert(root, "hell");
insert(root, "cat");
insert(root, "a");
insert(root, "hel");
insert(root, "help");
insert(root, "helps");
insert(root, "helping");
int comp = printAutoSuggestions(root, "hel");
if (comp == -1)
System.out.println("No other strings found "+
"with this prefix\n");
else if (comp == 0)
System.out.println("No string found with"+
" this prefix\n");
}
}

159
Others/Sudoku.java Normal file
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package Others;
class Sudoku
{
public static boolean isSafe(int[][] board,
int row, int col,
int num)
{
// Row has the unique (row-clash)
for (int d = 0; d < board.length; d++)
{
// Check if the number we are trying to
// place is already present in
// that row, return false;
if (board[row][d] == num) {
return false;
}
}
// Column has the unique numbers (column-clash)
for (int r = 0; r < board.length; r++)
{
// Check if the number
// we are trying to
// place is already present in
// that column, return false;
if (board[r][col] == num)
{
return false;
}
}
// Corresponding square has
// unique number (box-clash)
int sqrt = (int)Math.sqrt(board.length);
int boxRowStart = row - row % sqrt;
int boxColStart = col - col % sqrt;
for (int r = boxRowStart;
r < boxRowStart + sqrt; r++)
{
for (int d = boxColStart;
d < boxColStart + sqrt; d++)
{
if (board[r][d] == num)
{
return false;
}
}
}
// if there is no clash, it's safe
return true;
}
public static boolean solveSudoku(
int[][] board, int n)
{
int row = -1;
int col = -1;
boolean isEmpty = true;
for (int i = 0; i < n; i++)
{
for (int j = 0; j < n; j++)
{
if (board[i][j] == 0)
{
row = i;
col = j;
// We still have some remaining
// missing values in Sudoku
isEmpty = false;
break;
}
}
if (!isEmpty) {
break;
}
}
// No empty space left
if (isEmpty)
{
return true;
}
// Else for each-row backtrack
for (int num = 1; num <= n; num++)
{
if (isSafe(board, row, col, num))
{
board[row][col] = num;
if (solveSudoku(board, n))
{
// print(board, n);
return true;
}
else
{
// replace it
board[row][col] = 0;
}
}
}
return false;
}
public static void print(
int[][] board, int N)
{
// We got the answer, just print it
for (int r = 0; r < N; r++)
{
for (int d = 0; d < N; d++)
{
System.out.print(board[r][d]);
System.out.print(" ");
}
System.out.print("\n");
if ((r + 1) % (int)Math.sqrt(N) == 0)
{
System.out.print("");
}
}
}
// Driver Code
public static void main(String args[])
{
int[][] board = new int[][] {
{ 3, 0, 6, 5, 0, 8, 4, 0, 0 },
{ 5, 2, 0, 0, 0, 0, 0, 0, 0 },
{ 0, 8, 7, 0, 0, 0, 0, 3, 1 },
{ 0, 0, 3, 0, 1, 0, 0, 8, 0 },
{ 9, 0, 0, 8, 6, 3, 0, 0, 5 },
{ 0, 5, 0, 0, 9, 0, 6, 0, 0 },
{ 1, 3, 0, 0, 0, 0, 2, 5, 0 },
{ 0, 0, 0, 0, 0, 0, 0, 7, 4 },
{ 0, 0, 5, 2, 0, 6, 3, 0, 0 }
};
int N = board.length;
if (solveSudoku(board, N))
{
// print solution
print(board, N);
}
else {
System.out.println("No solution");
}
}
}

66
Strings/List_all_Possible_Words_From_Phone_Digits.java Normal file
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package Strings;
import java.util.*;
import java.lang.*;
import java.io.*;
public class List_all_Possible_Words_From_Phone_Digits {
static Character[][] numberToCharMap;
private static List<String> printWords(int[] numbers,
int len,
int numIndex,
String s)
{
if(len == numIndex)
{
return new ArrayList<>(Collections.singleton(s));
}
List<String> stringList = new ArrayList<>();
for(int i = 0;
i < numberToCharMap[numbers[numIndex]].length; i++)
{
String sCopy =
String.copyValueOf(s.toCharArray());
sCopy = sCopy.concat(
numberToCharMap[numbers[numIndex]][i].toString());
stringList.addAll(printWords(numbers, len,
numIndex + 1,
sCopy));
}
return stringList;
}
private static void printWords(int[] numbers)
{
generateNumberToCharMap();
List<String> stringList =
printWords(numbers, numbers.length, 0, "");
stringList.stream().forEach(System.out :: println);
}
private static void generateNumberToCharMap()
{
numberToCharMap = new Character[10][5];
numberToCharMap[0] = new Character[]{'\0'};
numberToCharMap[1] = new Character[]{'\0'};
numberToCharMap[2] = new Character[]{'a','b','c'};
numberToCharMap[3] = new Character[]{'d','e','f'};
numberToCharMap[4] = new Character[]{'g','h','i'};
numberToCharMap[5] = new Character[]{'j','k','l'};
numberToCharMap[6] = new Character[]{'m','n','o'};
numberToCharMap[7] = new Character[]{'p','q','r','s'};
numberToCharMap[8] = new Character[]{'t','u','v'};
numberToCharMap[9] = new Character[]{'w','x','y','z'};
}
// Driver code
public static void main(String[] args)
{
int number[] = {2, 3, 4};
printWords(number);
}
}