Naive sudoku solver

Sudoku.py

import cProfile
def row_check(i,j): return i//9==j//9
def col_check(i,j): return (i-j)%9==0
def blocks_check(i,j): return   i//27==j//27 and (i%9)//3==(j%9)//3

def show(grid): 
    print "".join(num+" "+" "*((i+1)%3==0)+"\n"*((i+1)%9==0) for i,num in enumerate(grid))


def solve(grid):

    i=grid.find("0")

    if i==-1: 
        show(grid)
        return 0  
    temp=set()
    for pos in range(81):
        if row_check(i,pos) or col_check(i,pos) or blocks_check(i,pos):
            temp.add(grid[pos])
    for num in digits:
        if num not in temp:
            solve(grid[:i]+num+grid[i+1:])
    return 0

grids ="026000810300708006400050007050107090003905100040302050100030002500204009038000460"

print "Given grid:"

show(grids)

print "Number of empty fields",grids.count("0")


print "Number of checks using bruteforce is > %18d"%grids.count("0")**9


digits="123456789"

print "Solution using backtracking :"
cProfile.run("solve(grids)")

"""
Outputs:
Given grid:
0 2 6  0 0 0  8 1 0  
3 0 0  7 0 8  0 0 6  
4 0 0  0 5 0  0 0 7  
0 5 0  1 0 7  0 9 0  
0 0 3  9 0 5  1 0 0  
0 4 0  3 0 2  0 5 0  
1 0 0  0 3 0  0 0 2  
5 0 0  2 0 4  0 0 9  
0 3 8  0 0 0  4 6 0  

Number of empty fields 47
Number of checks using bruteforce is >   1119130473102767
Solution using backtracking :
7 2 6  4 9 3  8 1 5  
3 1 5  7 2 8  9 4 6  
4 8 9  6 5 1  2 3 7  
8 5 2  1 4 7  6 9 3  
6 7 3  9 8 5  1 2 4  
9 4 1  3 6 2  7 5 8  
1 9 4  8 3 6  5 7 2  
5 6 7  2 1 4  3 8 9  
2 3 8  5 7 9  4 6 1  

         34792 function calls (34648 primitive calls) in 0.029 seconds

   Ordered by: standard name

   ncalls  tottime  percall  cumtime  percall filename:lineno(function)
        1    0.000    0.000    0.029    0.029 <string>:1(<module>)
    145/1    0.016    0.000    0.029    0.029 sud.py:11(solve)
    11664    0.004    0.000    0.004    0.000 sud.py:3(row_check)
    10368    0.004    0.000    0.004    0.000 sud.py:4(col_check)
     9216    0.004    0.000    0.004    0.000 sud.py:5(blocks_check)
        1    0.000    0.000    0.000    0.000 sud.py:7(show)
       82    0.000    0.000    0.000    0.000 sud.py:8(<genexpr>)
     3024    0.001    0.000    0.001    0.000 {method 'add' of 'set' objects}
        1    0.000    0.000    0.000    0.000 {method 'disable' of '_lsprof.Profiler' objects}
      145    0.000    0.000    0.000    0.000 {method 'find' of 'str' objects}
        1    0.000    0.000    0.000    0.000 {method 'join' of 'str' objects}
      144    0.000    0.000    0.000    0.000 {range}




"""


"""
/*
The C++ Version of the above code
*/
#include"bits/stdc++.h"

using namespace std;

int check_row(int i ,int j){
    return i/9==j/9;
    }

int check_col(int i, int j){
    return (i-j)%9==0;
    }
int check_block(int i , int j){
    return i/27==j/27 && (i%9)/3==(j%9)/3 ;
    }

int solve(char *x){

    int i=0,cur=-1;
    for (i=0;x[i]!='\0';i++){
            if(x[i]=='0'){
                    cur=i;
                    break;
            }
    }
    if(cur==-1){
        int l=0;
        for(l=0;l<81;l++){
            printf("%c ",x[l]);
            if((l+1)%3==0)printf(" ");
            if((l+1)%9==0)puts("");
        }

        return 0;
    }
    set<char> myset;
    myset.clear();
    for(int k=0;k<81;k++){
            if(check_row(cur,k)||check_col(cur,k)||check_block(cur,k)){
                myset.insert(x[k]);
            }
    }
    char d[10]="123456789";
    int j=0;
    for (j=0;j<9;j++){
      if(d[j]!=(*myset.find(d[j]))){
        char temp[82];
            for(int n=0;n<81;n++){
                temp[n]=(n==i?d[j]:x[n]);
            }

        solve(temp);
        }


    }
}

int main(){
    char grids[82] ="026000810300708006400050007050107090003905100040302050100030002500204009038000460";
    int o=0;
    for(o=0;o<81;o++){
        printf("%c ",grids[o]);
        if((o+1)%3==0)printf(" ");
        if((o+1)%9==0)puts("");
    }
    puts("");
    cout<<"Solution: d"<<endl;
    solve(grids);
}
"""