Add step4

step4

@@ -0,0 +1,255 @@
+#include <stdio.h>
+#include <time.h>
+#include <stdlib.h>
+int main()
+{
+	int g=0,h=0,l;
+	int i,j,d,f=1,p,q,m,z,y=1,x=1,c=0,k=1,u,v,w=0;
+	int board[9][9] = {{5, 3, 0, 0, 7, 0, 0, 0, 0}, 
+	{6, 0, 0, 1, 9, 5, 0, 0, 0}, 
+	{0, 9, 8, 0, 0, 0, 0, 6, 0}, 
+	{8, 0, 0, 0, 6, 0, 0, 0, 3}, 
+	{4, 0, 0, 8, 0, 3, 0, 0, 1}, 
+	{7, 0, 0, 0, 2, 0, 0, 0, 6}, 
+	{0, 6, 0, 0, 0, 0, 2, 8, 0}, 
+	{0, 0, 0, 4, 1, 9, 0, 0, 5}, 
+	{0, 0, 0, 0, 8, 0, 0, 7, 9}};
+	//这个位置加下original matrix的格式输出 ，变量i,j可用 
+	
+		printf("The original Sudoku matrix:\n");
+	printf("|");
+	for(int i=0;i<23;i++)
+	{
+		printf("-");
+	}
+	printf("|");
+	printf("\n");
+	for(int i=0;i<9;i++)
+	{
+		printf("| ");
+		for(int j=0;j<9;j++)
+		{
+		    printf("%d ",board[i][j]);
+		    if(j==2||j==5||j==8)
+		    {
+			    printf("| ");
+		    }
+		}
+	    printf("\n");
+	    if((i+1)%3==0&&i!=0)
+	    {
+		    printf("| ");
+		    for(int k=1;k<23;k++)
+		    {
+			     printf("-");
+		    }
+		    printf("|");
+		    printf("\n");
+	    }
+	}
+
+	int a[10],b[100];
+	f=1;
+	for(i=0;i<9;i++)
+	{
+		for(j=0;j<10;j++)
+		{
+			a[j]=0;
+		}
+		for(j=0;j<9;j++)
+		{
+			d=board[j][i];
+			a[d-1]++;
+			if(a[d-1]>=2&&d-1!=-1) 
+			{
+				f=0;u=d;v=i;w=1;
+			}
+		} 
+	} 
+	for(i=0;i<9;i++)
+	{
+		for(j=0;j<10;j++)
+		{
+			a[j]=0;
+		}
+		for(j=0;j<9;j++)
+		{
+			d=board[i][j];
+			a[d-1]++;
+			if(a[d-1]>=2&&d-1!=-1) 
+			{
+				f=0;u=d;v=i;w=2;
+			}
+		} 
+	} 
+	for (p=0;p<3;p++)
+	{
+		for(q=0;q<3;q++)
+		{
+			for(m=0;m<10;m++)
+			{
+				a[m]=0;
+			}
+			for (i=3*p;i<3*p+3;i++)
+			{
+				for(j=3*q;j<3*q+3;j++)
+				{
+					d=board[i][j];
+					a[d-1]++;
+					if(a[d-1]>=2&&d-1!=-1) 
+					{
+						f=0;u=d;v=3*p+q+1;w=3;
+					}
+				}
+			}
+		}
+	}
+	if(f==1) printf("True:Valid initial Sudoku matrix!\n");
+	else {
+		printf("False:Invalid initial Sudoku matrix!\n");
+		return 0;
+    }
+	if(w==1) printf("The number %d in the line %d has been used!",x,y);
+	else if(w==2) printf("The number %d in the col %d has been used!",x,y);
+	else if(w==3) printf("The number %d in the block %d has been used!",x,y);
+
+	b[0]=10;
+	for (i=0;i<9;i++)
+	{
+		for(j=0;j<9;j++)
+		{
+			if (board[i][j]==0)
+			{
+				b[x]=10*i+j;
+				x++;
+			}
+		}
+	}
+	
+	z=x;
+	x=1;
+	while (x<z)				
+	{
+		l=c+1;
+		h=b[x]/10;
+		g=b[x]%10;
+		while (l<=9)
+		{
+			
+			f=1;
+			board[h][g]=l;
+			for(i=0;i<9;i++)
+			{
+				for(j=0;j<10;j++)
+				{
+					a[j]=0;
+				}
+				for(j=0;j<9;j++)
+				{
+					d=board[j][i];
+					a[d-1]++;
+					if(a[d-1]>=2&&d!=0) 
+					{
+						f=0;
+					}
+				} 
+			} 
+			for(i=0;i<9;i++)
+			{
+				for(j=0;j<10;j++)
+				{
+					a[j]=0;
+				}
+				for(j=0;j<9;j++)
+				{
+					d=board[i][j];
+					a[d-1]++;
+					if(a[d-1]>=2&&d!=0) 
+					{
+						f=0;
+					}
+				} 
+			} 
+			for (p=0;p<3;p++)
+			{
+				for(q=0;q<3;q++)
+				{
+					for(m=0;m<10;m++)
+					{
+						a[m]=0;
+					}
+					for (i=3*p;i<3*p+3;i++)
+					{
+						for(j=3*q;j<3*q+3;j++)
+						{
+							d=board[i][j];
+							a[d-1]++;
+							if(a[d-1]>=2&&d!=0) 
+							{
+								f=0;
+							}
+						}
+			
+					}
+				}	
+			} 
+			if (f==0) l++;
+			else  break;
+		}	
+			
+		if (l==10&&f==0) 
+		{
+			board[h][g]=0;
+			x--;
+			h=b[x]/10;
+			g=b[x]%10;
+			c=board[h][g];
+		}
+		else 
+		{
+			x++;c=0;
+		}
+		if(x==0) 
+		{
+			k=0;
+			break;
+		}
+	}
+	if (k==0) printf("No solution!");
+	else 
+	{
+		printf("The solution of Sudoku matrix:\n");
+		//这个位置也需要The solution of Sudoku matrix:的格式化输出 
+		printf("|");
+		for(int i=0;i<23;i++)
+		{
+			printf("-");
+		}
+		printf("|");
+		printf("\n");
+		for(int i=0;i<9;i++)
+		{
+			printf("| ");
+			for(int j=0;j<9;j++)
+			{
+		    	printf("%d ",board[i][j]);
+		    	if(j==2||j==5||j==8)
+		    	{
+			    	printf("| ");
+		    	}
+			}
+	    	printf("\n");
+	    	if((i+1)%3==0&&i!=0)
+	    	{
+		    	printf("| ");
+		    	for(int k=1;k<23;k++)
+		    	{
+			    	printf("-");
+		    	}
+		    	printf("|");
+		    	printf("\n");
+	    	}
+		}
+	}
+	return 0;
+}