Go: package main

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

var scanner = bufio.NewScanner(os.Stdin)

func main() {
	scanner.Split(bufio.ScanWords)
	for scanner.Scan() {
		table := [9][9]int{}
		check := [9][9]bool{}
		n, _ := strconv.Atoi(scanner.Text())
		for n > 0 {
			n--
			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()
			}
		}
	}
}

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

C++: #include<iostream>
using namespace std;
int main(){
  int n;
  cin >>n;
  while(n--){
    int field[9][9] = {0};
    bool flag[9][9] = {false};
    for(int i=0; i<9; i++){
      for(int j=0; j<9; j++){
	cin >>field[i][j];
      }
    }
    for(int i=0; i<9; i++){
      int log[10] = {0};
      for(int j=0; j<9; j++){
	if(log[field[i][j]] != 0){flag[i][j] = true;flag[i][log[field[i][j]]-1] = true;}
	log[field[i][j]] = j+1;
      }
    }
    for(int i=0; i<9; i++){
      int log[10] = {0};
      for(int j=0; j<9; j++){
	if(log[field[j][i]] != 0){flag[j][i] = true;flag[log[field[j][i]]-1][i] = true;}
	log[field[j][i]] = j+1;
      }
    }
    for(int i=0; i<9; i++){
      int log[10] = {0};
      for(int j=0; j<9; j++){
	if(log[field[j%3+(i%3)*3][j/3+(i/3)*3]] != 0){
	  int r = log[field[j%3+(i%3)*3][j/3+(i/3)*3]]-1;
	  flag[j%3+(i%3)*3][j/3+(i/3)*3] = true;
	  flag[r%3+(i%3)*3][r/3+(i/3)*3] = true;
	}
	log[field[j%3+(i%3)*3][j/3+(i/3)*3]] = j+1;
      }
    }
    for(int i=0; i<9; i++){
      for(int j=0; j<9; j++){
	if(flag[i][j]){cout <<"*";}
	else{cout <<" ";}
	cout <<field[i][j];
      }
      cout <<endl;
    }
  }
  return 0;
}

C++: #include<iostream>
#include<cstring>
using namespace std;
int x[9][9], n, s[10], cnt[10], p[9][9]; bool a[9][9];
int main() {
	cin >> n;
	for (int i = 0; i < n; i++) {
		memset(x, 0, sizeof(x));
		memset(p, 0, sizeof(p));
		memset(a, false, sizeof(a));
		memset(cnt, 0, sizeof(cnt));
		if (i) { cout << endl; }
		for (int j = 0; j < 9; j++) {
			for (int k = 0; k < 9; k++) {
				cin >> x[j][k];
			}
		}
		for (int j = 0; j < 9; j++) {
			memset(s, 0, sizeof(s));
			for (int k = 0; k < 9; k++) {
				s[x[j][k]]++;
			}
			for (int k = 0; k < 9; k++) {
				if (s[x[j][k]] >= 2) {
					a[j][k] = true;
				}
			}
		}
		for (int j = 0; j < 9; j++) {
			memset(s, 0, sizeof(s));
			for (int k = 0; k < 9; k++) {
				s[x[k][j]]++;
			}
			for (int k = 0; k < 9; k++) {
				if (s[x[k][j]] >= 2) {
					a[k][j] = true;
				}
			}
		}
		for (int j = 0; j < 9; j++) {
			for (int k = 0; k < 9; k++) {
				p[(j / 3) * 3 + (k / 3)][cnt[(j / 3) * 3 + (k / 3)]] = x[j][k];
				cnt[(j / 3) * 3 + (k / 3)]++;
			}
		}
		for (int j = 0; j < 9; j++) {
			memset(s, 0, sizeof(s));
			for (int k = 0; k < 9; k++) {
				s[p[j][k]]++;
			}
			for (int k = 0; k < 10; k++) {
				if (s[p[j][k]] >= 2) {
					for (int l = 0; l < 9; l++) {
						if (x[j][k] == p[j][k]) {
							a[j][k] = true;
						}
					}
				}
			}
		}
		for (int j = 0; j < 9; j++) {
			for (int k = 0; k < 9; k++) {
				if (a[j][k] == true) {
					cout << '*';
				}
				else {
					cout << ' ';
				}
				cout << x[j][k];
			}
			cout << endl;
		}
	}
}

C++: #define _crt_secure_no_warnings

#ifndef _GLIBCXX_NO_ASSERT
#include <cassert>
#endif
#include <cctype>
#include <cerrno>
#include <cfloat>
#include <ciso646>
#include <climits>
#include <clocale>
#include <cmath>
#include <csetjmp>
#include <csignal>
#include <cstdarg>
#include <cstddef>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>

#ifdef __GXX_EXPERIMENTAL_CXX0X__
#include <ccomplex>
#include <cfenv>
#include <cinttypes>
#include <cstdbool>
#include <cstdint>
#include <ctgmath>
#include <cwchar>
#include <cwctype>
#endif


#include <algorithm>
#include <bitset>
#include <complex>
#include <deque>
#include <exception>
#include <fstream>
#include <functional>
#include <iomanip>
#include <ios>
#include <iosfwd>
#include <iostream>
#include <istream>
#include <iterator>
#include <limits>
#include <list>
#include <locale>
#include <map>
#include <memory>
#include <new>
#include <numeric>
#include <ostream>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <stdexcept>
#include <streambuf>
#include <string>
#include <typeinfo>
#include <utility>
#include <valarray>
#include <vector>

#ifdef __GXX_EXPERIMENTAL_CXX0X__
#include <array>
#include <atomic>
#include <chrono>
#include <condition_variable>
#include <forward_list>
#include <future>
#include <initializer_list>
#include <mutex>
#include <random>
#include <ratio>
#include <regex>
#include <system_error>
#include <thread>
#include <tuple>
#include <typeindex>
#include <type_traits>
#include <unordered_map>
#include <unordered_set>
#endif


using namespace std;

int main()
{
	int N;
	cin >> N;
	for (size_t p = 0; p < N; p++)
	{
		int data[9][9];
		bool ans[9][9] = {};
		for (size_t i = 0; i < 9; i++)
		{
			for (size_t j = 0; j < 9; j++)
			{
				cin >> data[i][j];
				data[i][j]--;
			}
		}
		for (size_t i = 0; i < 9; i++)
		{
			int a[9] = {}, b[9] = {};
			for (size_t j = 0; j < 9; j++)
			{
				a[data[i][j]]++;
				b[data[j][i]]++;
			}
			for (size_t j = 0; j < 9; j++)
			{
				if (a[j] != 1)
				{
					for (size_t k = 0; k < 9; k++)
					{
						if (data[i][k] == j)
						{
							ans[i][k] = 1;
						}
					}
				}
				if (b[j] != 1)
				{
					for (size_t k = 0; k < 9; k++)
					{
						if (data[k][i] == j)
						{
							ans[k][i] = 1;
						}
					}
				}
			}
		}
		for (size_t i = 0; i < 3; i++)
		{
			for (size_t j = 0; j < 3; j++)
			{
				int c[9] = {};
				for (size_t k = 0; k < 3; k++)
				{
					for (size_t l = 0; l < 3; l++)
					{
						c[data[i * 3 + k][j * 3 + l]]++;
					}
				}
				for (size_t k = 0; k < 9; k++)
				{
					if (c[k] != 1)
					{
						for (size_t l = 0; l < 3; l++)
						{
							for (size_t m = 0; m < 3; m++)
							{
								if (data[i * 3 + l][j * 3 + m] == k)
								{
									ans[i * 3 + l][j * 3 + m] = 1;
								}
							}
						}
					}
				}
			}
		}
		for (size_t i = 0; i < 9; i++)
		{
			for (size_t j = 0; j < 9; j++)
			{
				cout << (ans[i][j] ? "*" : " ") << data[i][j] + 1;
			}
			cout << endl;
		}
		if (p != N - 1)
		{
			cout << endl;
		}
	}
	return 0;
}

C++: #include <iostream>

using namespace std;

int p[9][9];

int as(int, int);
int sq(int, int);

int main() {

	int n;

	cin >> n;
	for(int c=0; c<n; c++) {
		if(c) {
			cout << endl;
		}
		for(int i=0; i<9; i++) {
			for(int j=0; j<9; j++) {
				cin >> p[i][j];
			}
		}
							
		for(int i=0; i<9; i++) {
			for(int j=0; j<9; j++) {
				cout << ((as(i, j)||sq(i, j)) ? "*" : " ") << p[i][j];
			}
			cout << endl;
		}
	}

	return 0;

}


int as(int i, int j) {

	int f=0;

	for(int k=0; k<9; k++) {
		if((p[i][j]==p[k][j]||p[i][j]==p[i][k])&&!(i==k||j==k)) {
			f++;
		}
	}
	return (f ? 1 : 0);

}

int sq(int i, int j) {

	int f=0, x=(i/3)*3, y=(j/3)*3;

	for(int k=x; k<x+3; k++) {
		for(int l=y; l<y+3; l++) {
			if(p[i][j]==p[k][l]&&!(i==k&&j==l)) {
				f++;
			}
		}
	}
	if(f) {
		return 1;
	}
	return 0;

}