Go: package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
)

var scanner = bufio.NewScanner(os.Stdin)

func main() {
	scanner.Split(bufio.ScanWords)
	scanner.Scan()
	table := [9][9]int{}
	check := [9][9]bool{}
	n, _ := strconv.Atoi(scanner.Text())
	for n > 0 {
		for i := 0; i < 9; i++ {
			for j := 0; j < 9; j++ {
				table[i][j] = nextInt()
			}
		}
		for i := 0; i < 9; i++ {
			for j := 0; j < 9; j++ {
				ok := true
				for k := 0; k < 9; k++ {
					if table[i][j] == table[i][k] && j != k {
						ok = false
					}
				}
				for k := 0; k < 9; k++ {
					if table[i][j] == table[k][j] && i != k {
						ok = false
					}
				}
				seci := i / 3
				secj := j / 3
				for k := 0; k < 3; k++ {
					for l := 0; l > 3; l++ {
						if table[seci*3+k][secj*3+l] == table[i][j] && seci*3+k != i && secj*3+l != j {
							ok = false
						}
					}
				}
				if !ok {
					check[i][j] = true
				}
			}
		}
		for i := 0; i < 9; i++ {
			for j := 0; j < 9; j++ {
				if check[i][j] {
					fmt.Print("*")
				} else {
					fmt.Print(" ")
				}
				fmt.Print(table[i][j])
			}
			fmt.Println()
		}
		if n != 0 {
			fmt.Println()
		}
		n--
	}
}

func nextInt() int {
	scanner.Scan()
	i, e := strconv.Atoi(scanner.Text())
	if e != nil {
		panic(e)
	}
	return i
}

C++: # define _CRT_SECURE_NO_WARNINGS 1
# include <iostream>
# include <string>
# include <bitset>
# include <vector>
# include <algorithm>
# include <cstdlib>
# include <cstdio>
# include <cstring>
# include <cstdlib>
# include <iomanip>
# include <queue>
# include <sstream>
# include <climits>
# include <cmath>
# include <list>
# include <functional>
# include <string>
# include <ctime>
# include <set>
# include <map>
# include <stack>
# include <unordered_map>
using namespace std;
//# define M_PI 3.141592
# define INF ((int)(1<<30))
# define FOR(i,n) for(int i=0;i<(int)n;i++)
# define FORI(i,k,n) for(int i=k;i<(int)n;i++)
# define toRad 2.0*M_PI/360.0
# define inin(x) int x;cin>>x;
# define all(x) x.begin(),x.end()
# define debug(x) cout<<#x<<" :"<<x<<endl;
# define rep(i,n) for(int i=0;i<(int)n;i++)
# define EPS 1e-12
# define CHECK(i,a) FOR(i,a.size())cout<<#a<<"["<<i<<"] : "<<a[i]<<endl; 

int main()
{
	int n; cin >> n;
	bool f = false;
	while (n--)
	{
		if (f)cout << endl;
		f = true;
		int a[9][9];
		bool b[9][9];
		for (int i = 0; i < 9; i++)
		{
			for (int j = 0; j < 9; j++)
			{
				cin >> a[i][j];
				b[i][j] = false;
			}
		}
		for (int i = 0; i < 9; i++)
		{
			for (int j = 0; j < 9; j++)
			{


				for (int k = 0; k < 9; k++)
				{
					if (k == j)continue;
					if (a[i][j] == a[i][k])
					{
						b[i][j] = true;
						b[i][k] = true;
					}
					if (a[j][i] == a[k][i])
					{
						b[j][i] = true;
						b[k][i] = true;
					}
				}
				if (i % 3 == 0 && j % 3 == 0)
				{
					for (int k = 0; k < 9; k++)
					{
						for (int l = 0; l < 9; l++)
						{
							if (i + k % 3 == i + l % 3 || j + k / 3 == j + l / 3)continue;
							if (a[i + k % 3][j + k / 3] == a[i + l % 3][j + l / 3])
							{
								b[i + k % 3][j + k / 3] = true;
								b[i + l % 3][j + l / 3] = true;
							}
						}
					}
				}

			}
		}

		for (int i = 0; i < 9; i++)
		{
			for (int j = 0; j < 9; j++)
			{
				cout << (b[i][j] ? '*' : ' ');
				cout << a[i][j];
			}
			cout << endl;
		}
	}


}

C++: #include <iostream>
#include <cstdio>

using namespace std;

int puzzle[10][10];
int col[10][10], row[10][10]; // 列，行
bool check[10][10];  // 間違っている場合はfalse
int n;

/*
  rect[0] rect[1] rect[2]
  rect[3] rect[4] rect[5]
  rect[6] rect[7] rect[8]
*/
int rect[10][10];

void solve()
{
    // 行・列のチェック
    for (int i = 0; i < 9; i++) {
        for (int j = 0; j < 9; j++) {
            // 列のチェック
            if (col[j][puzzle[i][j] - 1] != -1) {
                int bf = col[j][puzzle[i][j] - 1];
                check[bf][j] = check[i][j] = false;
                col[j][puzzle[i][j] - 1] = i;
            }
            else
                col[j][puzzle[i][j] - 1] = i;

            // 行のチェック
            if (row[i][puzzle[i][j] - 1] != -1) {
                int bf = row[i][puzzle[i][j] - 1];
                check[i][bf] = check[i][j] = false;
                row[i][puzzle[i][j] - 1] = j;
            }
            else
                row[i][puzzle[i][j] - 1] = j;
        }
    }

    // 3x3の領域のチェック
    for (int i = 0; i < 9; i++) {
        for (int j = 0; j < 3; j++) {
            for (int k = 0; k < 3; k++) {
                int x = (i % 3) * 3 + k;
                int y = (i / 3) * 3 + j;

                if (rect[i][puzzle[y][x] - 1] != -1) {
                    int nx = (i % 3) * 3 + (rect[i][puzzle[y][x] - 1] % 3);
                    int ny = (i / 3) * 3 + (rect[i][puzzle[y][x] - 1] / 3);

                    check[ny][nx] = check[y][x] = false;
                    rect[i][puzzle[y][x] - 1] = j * 3 + k;
                }
                else
                    rect[i][puzzle[y][x] - 1] = j * 3 + k;                    
            }
        }
    }

    for (int i = 0; i < 9; i++)
        for (int j = 0; j < 9; j++) {
            if (check[i][j]) 
                printf(" %d", puzzle[i][j]);
            else
                printf("*%d", puzzle[i][j]);
            
            if (j + 1 == 9)
                putchar('\n');
        }
}

int main()
{
    cin >> n;
    for (int i = 0; i < n; i++) {
        for (int j = 0; j < 9; j++)
            for (int k = 0; k < 9; k++) {
                cin >> puzzle[j][k];
                col[j][k] = row[j][k] = rect[j][k] = -1;
                check[j][k] = true;
            }

        if (i != 0)
            putchar('\n');
        solve();
    }
        

    return 0;
}

C++: #include<iostream>
#include<algorithm>
#include<climits>
#include<cmath>
#include<cstdio>
#include<cstdlib>
#include<ctime>
#include<string>
#include<cstring>
#include<vector>
#include<stack>
#include<queue>
#include<set>
#include<map>
#include<bitset>

using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> i_i;

#define PI 3.141592653589793238462643383279
#define mod 1000000007LL
#define rep(i, n) for(i = 0;i < n;++i)
#define rep1(i, n) for(i = 1;i < n;++i)
#define per(i, n) for(i = n - 1;i > -1;--i)
#define int(x) int x; scanf("%d",&x)
#define int2(x, y) int x, y; scanf("%d%d",&x, &y)
#define int3(x, y, z) int x, y, z; scanf("%d%d%d",&x, &y, &z)
#define int4(v, x, y, z) int v, x, y, z; scanf("%d%d%d%d", &v, &x, &y, &z)
#define int5(v, w, x, y, z) int v, w, x, y, z; scanf("%d%d%d%d%d", &v, &w, &x, &y, &z)
#define ll2(x, y) ll x, y; cin >> x >> y;
#define scn(n, a) rep(i, n)cin >> a[i]
#define sc2n(n, a, b) rep(i, n)cin >> a[i] >> b[i]
#define pri(x) cout << (x) << "\n"
#define pri2(x, y) cout << (x) << " " << (y) << "\n"
#define pri3(x, y, z) cout << (x) << " " << (y) << " " << (z) << "\n"
#define pb push_back
#define mp make_pair
#define all(a) (a).begin(),(a).end()
#define endl "\n"
#define kabe puts("---------------------------")
#define kara puts("")
#define debug(x) cout << " --- " << (x) << "\n"
#define debug2(x, y) cout << " --- " << (x) << " " << (y) << "\n"
#define debug3(x, y, z) cout << " --- " << (x) << " " << (y) << " " << (z) << "\n"
#define X first
#define Y second
#define eps 0.0001
#define prid(x) printf("%.15lf\n", x)

int f[9][9];
int dh[9] = {0, 0, 0, 1, 1, 1, 2, 2, 2};
int dw[9] = {0, 1, 2, 0, 1, 2, 0, 1, 2};

signed main(void){
  int i, j, k, l, m;
  int(n);
  for(int testcase = 0;testcase < n;testcase++){
    if(testcase != 0)puts("");
    rep(i, 9)rep(j, 9)scanf("%d", &f[i][j]);
    rep(i, 9){
      rep(j, 9){
        bool is = true;
        rep(k, 9){
          if(i != k)if(f[i][j] == f[k][j])is = false;
          if(j != k)if(f[i][j] == f[i][k])is = false;
          if(i % 3 != dh[k] && j % 3 != dw[k])
          if(f[i][j] == f[i / 3 * 3 + dh[k]][j / 3 * 3 + dw[k]])is = false;
        }
        if(is)printf(" %d", f[i][j]);
        else printf("*%d", f[i][j]);
      }
      puts("");
    }


//*/

//*/ break;
  }
  return 0;
}