# Sudoku backtracking problem

I’m only getting the first subgrid solved in the output, can anyone point out what’s wrong here?

``````#include <bits/stdc++.h>
#define vi vector<int>
#define dvi vector<vector<int>>
#define b begin
#define e end
#define ff first
#define ss second
#define viit vector<int>::iterator

using namespace std;

void peek (dvi vec) {
for(auto i:vec) {
for(auto j:i) cout << j;
cout << endl;
}
}

vi options (dvi grid, int i, int j, int n) {
vi o_vec;
if(grid[i][j]) return o_vec;
for(int m=1;m<=9;m++) o_vec.push_back(m);
for(int x=0;x<n;x++) {
viit it = find(o_vec.b(),o_vec.e(),grid[x][j]);
if(it!=o_vec.e()) o_vec.erase(it);
}
for(int y=0;y<n;y++) {
viit it = find(o_vec.b(),o_vec.e(),grid[i][y]);
if(it!=o_vec.e()) o_vec.erase(it);
}
int d=3;
int sub = n/d, si = (i/sub)*sub, sj = (j/sub)*sub;
for(int x=si;x<si+sub;x++) {
for(int y=sj;y<sj+sub;y++) {
viit it = find(o_vec.b(),o_vec.e(),grid[x][y]);
if(it!=o_vec.e()) o_vec.erase(it);
}
}
return o_vec;
}

bool sudoku (dvi& grid, int j, int n) {
if(j==n) return true;
else {
for(int i=0;i<n;i++) {
vi opt = options(grid,i,j,n);
if(opt.size()) {
for(int k=0;k<opt.size();k++) {
grid[i][j] = opt[k];
if(sudoku(grid,j+1,n)) return true;
}
grid[i][j] = 0;
}
}
}
return false;
}

void sudoku_util(dvi& grid) {
int n = grid.size();
sudoku(grid,0,n);
}

int main () {
dvi grid = {{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}};
sudoku_util(grid);
peek(grid);
return 0;
}
``````

Output:

``````316528490
529104706
487000031
003010080
900863005
050090600
130000250
000000074
005206300``````

can you please share the problem url so that I can understand the problem it looks cryptic

the unsolved sudoku is given in the main method, and the aim is to solve the sudoku by replacing all 0s by numbers from 1-9