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++: /*****include*****/
#include <iostream>
#include <set>
/*****デバッグ定義*****/
//#define DEBUG
/*****マクロ定義*****/

/*****名前空間*****/
using namespace std;

/*****グローバル変数置き場*****/

/*****その他関数置き場*****/

/*****main関数*****/
int main(){
/*****変数置き場*****/
	int n;
	int field[11][11];
	bool wrong[10];
	bool fail[11][11];
	int table_x[] = {0,1,2,0,1,2,0,1,2};
	int table_y[] = {0,0,0,1,1,1,2,2,2};
	set <int>appear;
	/*****処理部*****/
	cin >> n;
	while(n>0){
		n--;
		for(int i=0;i<11;i++)
			for(int j=0;j<11;j++){
				field[i][j] = 0;
				fail[i][j] = 0;
			}
		for(int i=0;i<10;i++)
			wrong[i] = false;
		for(int i=1;i<=9;i++)
			for(int j=1;j<=9;j++)
				cin >> field[i][j];
		appear.clear();
		
		for(int i=1;i<=9;i++){
			for(int j=1;j<=9;j++){
				if(appear.find(field[i][j]) != appear.end()){
					wrong[field[i][j]] = true;
				}else
					appear.insert(field[i][j]);
			}
			appear.clear();
			for(int k=1;k<=9;k++)
				if(wrong[field[i][k]])
					fail[i][k] = true;
			for(int k=0;k<10;k++){
				wrong[k] = false;
			}
		}
		for(int j=1;j<=9;j++){
			for(int i=1;i<=9;i++){
				if(appear.find(field[i][j]) != appear.end()){
					wrong[field[i][j]] = true;
				}else
					appear.insert(field[i][j]);
			}
			appear.clear();
			for(int k=1;k<=9;k++)
				if(wrong[field[k][j]])
					fail[k][j] = true;
			for(int k=0;k<10;k++){
				wrong[k] = false;
			}
		}

		for(int i=1;i<=9;i+=3)
			for(int j=1;j<=9;j+=3){
				for(int k=0;k<9;k++)
					if(appear.find(field[i+table_y[k]][j+table_x[k]]) != appear.end())
						wrong[field[i+table_y[k]][j+table_x[k]]] = true;
					else
						appear.insert(field[i+table_y[k]][j+table_x[k]]);
				appear.clear();
				for(int k=0;k<9;k++)
					if(wrong[field[i+table_y[k]][j+table_x[k]]])
						fail[i+table_y[k]][j+table_x[k]] = true;
				for(int k=0;k<10;k++){
					wrong[k] = false;
				}
			}
			
		for(int i=1;i<=9;i++){
			for(int j=1;j<=9;j++){
				if(fail[i][j])
					cout << "*";
				else
					cout << " ";
				cout << field[i][j];
			}
			cout << endl;
		}
		cout << endl;
	}
	/*****処理終了後*****/
	return 0;
}

C++: #include <bits/stdc++.h>
using namespace std;

// infty
#define ULLINF (ULLONG_MAX)
#define LLINF  (LLONG_MAX)
#define IINF   (INT_MAX)
#define INF    (1<<29)

// math
#define Sq(x) ((x)*(x))

// container utility
#define ALL(x) (x).begin(), (x).end()
#define MP make_pair
#define PB push_back
#define EACH(it,c) for(__typeof((c).begin())it=(c).begin();it!=(c).end();it++)

// rep
#define REP(i,a,b) for(int i=a;i<b;i++)
#define rep(i,n) REP(i,0,n)

// typedef
typedef pair<int, int> PII;
typedef vector<int> VI;
typedef vector<PII> VII;
typedef vector<VI> VVI;

typedef long long ll;

// pair util
#define FST first
#define SND second

// range validator
#define CK(n,a,b) (a<=n && n<b)

// conversion
template<class T> inline string toStr(T a) { ostringstream oss_; oss_ << a; return oss_.str(); }
inline int toInt(string s) { return atoi(s.c_str()); }

// prime
bool isPrime(int a) { for(int i=2; i*i <=a; i++) if(a%i == 0) return false; return true; }

int const dx[] = {-1,0,1,0,-1,1,1,-1};
int const dy[] = {0,-1,0,1,-1,-1,1,1};

//////////////////////////////////////////////////////////////


int main() {
  
  int N;
  bool blank = 0;
  cin >> N;
  rep(_, N) {
    if(blank) cout << endl;
    blank = 1;
    int arr[9][9] = {{}};
    char output[9][20] = {{}};
    VII star;
    for(int i=0; i<9; i++) {
      int used[10] = {};
      for(int j=0; j<9; j++) {
	cin >> arr[i][j];
	used[arr[i][j]] ++;
	output[i][2*j]   = ' ';
	output[i][2*j+1] = (char)('0' + arr[i][j]);
      }
      for(int j=0; j<9; j++){
	if(used[arr[i][j]] > 1) {
	  output[i][2*j] = '*';
	}
      }
    }
    
    for(int j=0; j<9; j++) {
      int used[10] = {};
      for(int i=0; i<9; i++) {
	used[arr[i][j]] ++;
      }
      for(int i=0; i<9; i++) {
	if(used[arr[i][j]] > 1) {
	  output[i][2*j] = '*';
	}
      }
    }
    
    for(int i=0; i<9; i++) {
      cout << output[i] << endl;
    }
    
  }
  return 0;
}

C++: #include<bits/stdc++.h>
using namespace std;

int n;
int board[9][9];
int dxy[3][3] = { { 0, 1, 2},
		  {-1, 0, 1},
		  {-2,-1, 0} };

bool cheak(int y,int x){
  for(int i=0;i<9;i++){
    if(i != y && board[y][x] == board[i][x]) return true;
    if(i != x && board[y][x] == board[y][i]) return true;
  }
  int py = y % 3;
  int px = x % 3;
  for(int i=0;i<3;i++){
    for(int j=0;j<3;j++){
      int nx = x+dxy[px][i];
      int ny = y+dxy[py][j];
      if(nx == x && ny == y) continue;
      if(board[y][x] == board[ny][nx]) return true;
    }
  }
  return false;
}

int main(){
  cin >> n;
  while(n--){
    for(int i=0;i<9;i++){
      for(int j=0;j<9;j++){
	cin >> board[i][j];
      }
    }
    for(int i=0;i<9;i++){
      for(int j=0;j<9;j++){
	if(cheak(i,j)) cout << "*" << board[i][j];
	else cout << " " << board[i][j];
      }
      cout << endl;
    }
    if(n != 0) cout << endl;
  }
}