Merge pull request AllAlgorithms#211 from AllAlgorithms/backtracking

Create crossword_puzzle.cpp

Author: abranhe

backtracking/crossword_puzzle.cpp

@@ -0,0 +1,171 @@
+#include <bits/stdc++.h> 
+using namespace std; 
+
+// ways are to calculate the number of 
+// possible ways to fill the grid 
+int ways = 0; 
+
+// this function is used to print 
+// the resultant matrix 
+void printMatrix(vector<string>& matrix, int n) 
+{ 
+for (int i = 0; i < n; i++) 
+cout << matrix[i] << endl; 
+} 
+
+// this function checks for the current word 
+// if it can be placed horizontally or not 
+// x -> it represent index of row 
+// y -> it represent index of column 
+// currentWord -> it represent the 
+// current word in word array 
+vector<string> checkHorizontal(int x, int y, 
+vector<string> matrix, 
+string currentWord) 
+{ 
+int n = currentWord.length(); 
+
+for (int i = 0; i < n; i++) { 
+if (matrix[x][y + i] == '#' || 
+matrix[x][y + i] == currentWord[i]) { 
+matrix[x][y + i] = currentWord[i]; 
+} 
+else { 
+
+// this shows that word cannot 
+// be placed horizontally 
+matrix[0][0] = '@'; 
+return matrix; 
+} 
+} 
+
+return matrix; 
+} 
+
+// this function checks for the current word 
+// if it can be placed vertically or not 
+// x -> it represent index of row 
+// y -> it represent index of column 
+// currentWord -> it represent the 
+// current word in word array 
+vector<string> checkVertical(int x, int y, 
+vector<string> matrix, 
+string currentWord) 
+{ 
+int n = currentWord.length(); 
+
+for (int i = 0; i < n; i++) { 
+if (matrix[x + i][y] == '#' || 
+matrix[x + i][y] == currentWord[i]) { 
+matrix[x + i][y] = currentWord[i]; 
+} 
+else { 
+
+// this shows that word 
+// cannot be placed vertically 
+matrix[0][0] = '@'; 
+return matrix; 
+} 
+} 
+return matrix; 
+} 
+
+// this function recursively checks for every 
+// word that can align vertically in one loop 
+// and in another loop it checks for those words 
+// that can align horizontally words -> it 
+// contains all the words to fill in a crossword 
+// puzzle matrix -> it contain the current 
+// state of crossword index -> it represent 
+// the index of current word n -> it represent 
+// the length of row or column of the square matrix 
+void solvePuzzle(vector<string>& words, 
+vector<string> matrix, 
+int index, int n) 
+{ 
+if (index < words.size()) { 
+string currentWord = words[index]; 
+int maxLen = n - currentWord.length(); 
+
+// loop to check the words that can align vertically. 
+for (int i = 0; i < n; i++) { 
+for (int j = 0; j <= maxLen; j++) { 
+vector<string> temp = checkVertical(j, i, 
+matrix, currentWord); 
+
+if (temp[0][0] != '@') { 
+solvePuzzle(words, temp, index + 1, n); 
+} 
+} 
+} 
+
+// loop to check the words that can align horizontally. 
+for (int i = 0; i < n; i++) { 
+for (int j = 0; j <= maxLen; j++) { 
+vector<string> temp = checkHorizontal(i, j, 
+matrix, currentWord); 
+
+if (temp[0][0] != '@') { 
+solvePuzzle(words, temp, index + 1, n); 
+} 
+} 
+} 
+} 
+else { 
+// calling of print function to 
+// print the crossword puzzle 
+cout << (ways + 1) << " way to solve the puzzle "
+<< endl; 
+printMatrix(matrix, n); 
+cout << endl; 
+
+// increase the ways 
+ways++; 
+return; 
+} 
+} 
+
+// Driver Code 
+int main() 
+{ 
+// length of grid 
+int n1 = 10; 
+
+// matrix to hold the grid of puzzle 
+vector<string> matrix; 
+
+// take input of puzzle in matrix 
+// input of grid of size n1 x n1 
+matrix.push_back("*#********"); 
+matrix.push_back("*#********"); 
+matrix.push_back("*#****#***"); 
+matrix.push_back("*##***##**"); 
+matrix.push_back("*#****#***"); 
+matrix.push_back("*#****#***"); 
+matrix.push_back("*#****#***"); 
+matrix.push_back("*#*######*"); 
+matrix.push_back("*#********"); 
+matrix.push_back("***#######"); 
+
+vector<string> words; 
+
+// the words matrix will hold all 
+// the words need to be filled in the grid 
+words.push_back("PUNJAB"); 
+words.push_back("JHARKHAND"); 
+words.push_back("MIZORAM"); 
+words.push_back("MUMBAI"); 
+
+// initialize the number of ways 
+// to solve the puzzle to zero 
+ways = 0; 
+
+// recursive function to solve the puzzle 
+// Here 0 is the initial index of words array 
+// n1 is length of grid 
+solvePuzzle(words, matrix, 0, n1); 
+cout << "Number of ways to fill the grid is "
+<< ways << endl; 
+
+return 0; 
+}