So I’ve been trying to store all the occurences of numbers from 1 to 9 in an array. I’ve succeeded for rows and columns and tried to apply the same logic for subgrids of 3×3 but to no avail.
My sudoku grid is a 2D array 9×9 (purposefully put two 9 in the same subgrid to trigger the error message).
0, 9, 0, 0, 0,,0, 0, 1, 0,
9, 0, 0, 0, 0, 0, 0, 0, 5,
8, 0, 5, 4, 0, 9, 2, 0, 7,
0, 0, 0, 3, 9, 6, 0, 0, 0,
0, 8, 0, 0, 0, 0, 0, 2, 0,
0, 0, 0, 2, 7, 8, 0, 0, 0,
3, 0, 7, 8, 0, 2, 5, 0, 9,
1, 0, 0, 0, 0, 0, 0, 0, 3,
0, 4, 0, 0, 0, 0, 0, 6, 0
Here’s the code of my function:
int no_conflict_3x3(int sudoku[N][N]){
int occurrence[N] = {0};
for (int l=0; l<3;l++){
for(int k = 0; k<3; k++){
for (int i=0+3*k; i<3*k; i++){
for(int j=0+3*l; j<3*l; j++){
printf("%d", sudoku[i][j]);
switch(sudoku[i][j]){
case 1:
occurrence[0]++;
break;
case 2:
occurrence[1]++;
break;
case 3:
occurrence[2]++;
break;
case 4:
occurrence[3]++;
break;
case 5:
occurrence[4]++;
break;
case 6:
occurrence[5]++;
break;
case 7:
occurrence[6]++;
break;
case 8:
occurrence[7]++;
break;
case 9:
occurrence[8]++;
break;
default:
break;
}
}
}
for (int o = 0; o<N; o++){
printf("o = %d : occurence=%d | ", o+1, occurrence[o]); //DEBUG
if (occurrence[o]>1){
printf("Not a valid sudoku grid.n");
return 1;}
else occurrence[o] = 0;
}
printf("n");
}
}
return 0;
}
and here’s the result after one iteration (for one line):
o = 1 : occurence=0 | o = 2 : occurence=0 | o = 3 : occurence=0 | o = 4 : occurence=0 | o = 5 : occurence=0 | o = 6 : occurence=0 | o = 7 : occurence=0 | o = 8 : occurence=0 | o = 9 : occurence=0 |
I don’t know why my variable occurrence is stuck at 0. Any help please?
6
You have 2 ignored loops since you loop from the start to the start.
Your i and j loops are like:
for (int i = 0; i < 0; ++i){...}
It does nothing.
Change
for (int i=0+3*k; i<3*k; i++){
for(int j=0+3*l; j<3*l; j++){
to:
for (int i=3*k; i<3*(k+1); i++){
for(int j=3*l; j<3*(l+1); j++){
Note the i < 3*k is changed to i < 3*(k + 1), similarly for j
On the other hand, you count the ‘golbal occurence’, but you need them in every 3×3 subgrid…
0
-
We need to reset
occurrences[]for every grid. -
We don’t need to count the occurrences of a number, if it’s a duplicate then we’ve an invalid grid (3×3)
-
We don’t need
switchcase, numbers themselves are good indexes intooccurrences[]
#include <stdio.h>
#include <unistd.h>
#define N 9
int no_conflict_3x3 (int sudoku[N][N]) {
// grids 3 x 3
for (int gri = 1; gri < N; gri += 3) { // grid row id
for (int gci = 1; gci < N; gci += 3) { // grid column id
int occurrence[N +1] = {0}; // +1 to use index [9]
for (int ri = gri -1; ri <= (gri +1); ++ri) {
for (int ci = gci -1; ci <= (gci +1); ++ci)
if (sudoku[ri][ci] && occurrence[sudoku[ri][ci]]) {
printf ("Invalid Grid, Grid Center [%d][%d].n", gri, gci);
return 1;
} else
occurrence[sudoku[ri][ci]] = 1;
}
for (int gi = 1; gi <= N; ++gi)
printf ("%d: occ %d | ", gi, occurrence[gi]);
putchar ('n');
}
}
return 0;
}
int main (void) {
int sudoku [N][N] = {
{0, 1, 4, 0, 0, 0, 0, 1, 0},
{9, 0, 0, 0, 0, 0, 0, 0, 5},
{8, 0, 5, 4, 0, 9, 2, 0, 7},
{0, 0, 0, 3, 9, 6, 0, 0, 0},
{0, 8, 0, 0, 0, 0, 0, 2, 0},
{0, 0, 0, 2, 7, 8, 0, 0, 0},
{3, 0, 7, 8, 0, 2, 5, 0, 9},
{1, 0, 0, 0, 0, 0, 0, 0, 3},
{0, 4, 0, 0, 0, 0, 0, 6, 5}
};
int status = no_conflict_3x3(sudoku);
return 0;
}