Create problem21.c

Author: rmkcodingclub

problem21.c

@@ -0,0 +1,114 @@
+//Solved by M Yuvasri, EEE
+
+#include<stdio.h>
+#include<stdlib.h>
+#define chessBoardSize 12
+ 
+int chessBoard[chessBoardSize][chessBoardSize] = {0};
+typedef struct point{
+    int x, y;
+}POINT;
+int count=0;
+ 
+int nextPosition(int x, int y, POINT* array){
+    int m=0;
+    /* finds the next possible points for the current
+    position in the chess board:
+    like
+    _   _   _   _   _   _
+    _   *   _   *   _   _
+    *   _   _   _   *   _
+    _   _   P   _   _   _
+    *   _   _   _   *   _
+    _   *   _   *   _   _ 
+ 
+as above if 'P' is the current (x,y)
+* represents the next possible points and
+also checks it exists within the chess board
+    */
+ 
+    if( (x+2) < chessBoardSize ){
+        if( (y+1) < chessBoardSize ){
+            array[m].x = x+2;
+            array[m++].y = y+1;
+        }
+        if( (y-1) >-1 ){
+            array[m].x = x+2;
+             array[m++].y = y-1;
+        }
+    }
+ 
+    if( (x-2) > -1){
+        if( (y+1) < chessBoardSize ){
+            array[m].x = x-2;
+            array[m++].y = y+1;
+        }
+        if( (y-1) >-1 ){
+            array[m].x = x-2;
+            array[m++].y = y-1;
+        }
+    }
+ 
+    if( (y+2) < chessBoardSize){
+        if( (x+1) < chessBoardSize ){
+            array[m].x = x+1;
+            array[m++].y = y+2;
+        }
+        if( (x-1) >-1 ){
+            array[m].x = x-1;
+            array[m++].y = y+2;    
+        }
+    }  
+ 
+    if( (y-2) > -1){
+        if( (x+1) < chessBoardSize ){
+            array[m].x = x+1;
+            array[m++].y = y-2;
+        }
+        if( (x-1) >-1 ){
+            array[m].x = x-1;
+            array[m++].y = y-2;    
+        }
+    }
+    return m;
+}
+ 
+void displayAnswer(){
+    int i, j, k;
+    printf("\n");
+    for(i=0; i<chessBoardSize; i++){
+        for(j=0; j<chessBoardSize; j++)
+            printf("%d\t",chessBoard[i][j]);
+            printf("\n\n");
+    }
+}
+ 
+//  recursive function using backtrack method
+void knightTravel(int x, int y){
+    POINT array[8] = {{0, 0}, {0, 0}};
+    // remainin initialized to zero automatically
+    volatile int noOfPossiblePoints = nextPosition(x, y, array);
+    volatile int i;
+ 
+    chessBoard[x][y] = ++count;
+ 
+    // base condition uses count
+    if( count == chessBoardSize * chessBoardSize ){
+        displayAnswer();
+        exit(0);
+    }
+ 
+    for(i=0; i< noOfPossiblePoints; i++)
+        if( chessBoard[array[i].x][array[i].y] == 0 )
+            knightTravel(array[i].x, array[i].y);
+ 
+    chessBoard[x][y] = 0;
+    count--;
+}
+ 
+int main()
+{
+    knightTravel(0, 0);
+    printf("No solution exists\n");
+    return 0;
+}