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 {
		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>
#include<string>
#include<cstdio>
#include<algorithm>
#include<stack>
#include<queue>
#include<vector>
#include<cmath>
#include<utility>
#include<set>
#include<complex>
#include<map>
#define vi vector<int>
#define vvi vector<vector<int> >
#define ll long long int
#define vl vector<ll>
#define vvl vector<vector<ll>>
#define vb vector<bool>
#define vc vector<char>
#define vs vector<string>
#define ld long double
#define INF 1e9
#define EPS 0.0000000001
#define rep(i,n) for(int i=0;i<n;i++)
#define loop(i,s,n) for(int i=s;i<n;i++)
#define CC puts("-------ok--------");
#define all(in) in.begin(), in.end()
using namespace std;
typedef pair<int, int> pii;
#define MAX 99999999
int main(){
    int n; cin>>n;
    rep(p,n){
    vector<vector<bool>>flag(10,vb(10,true));
    vvi v(10,vi(10,0));
    rep(i,9)rep(j,9)cin>>v[i][j];
    for(int i=0;i<9;i++){
        vb used(10,false);
        for(int j=0; j<9;j++){
            if(!used[v[i][j]]){used[v[i][j]]=true;}
            else {
                flag[i][j]=false;
                rep(k,9)if(v[i][k]==v[i][j])flag[i][k]=false;
            }
        }
    }
    for(int j=0;j<9;j++){
        vb used(10,false);
        for(int i=0; i<9;i++){
            if(!used[v[i][j]]){used[v[i][j]]=true;}
            else {
                flag[i][j]=false;
                rep(k,9)if(v[k][j]==v[i][j])flag[k][j]=false;
            }
        }
    }
   
    for(int h=0; h<=8;h+=3){
        for(int w=0; w<=8;w+=3){
            vb used(10,false);
            for(int i=h; i<h+3;i++){
                for(int j=w; j<w+3;j++){
                    if(!used[v[i][j]])used[v[i][j]]=true;
                    else for(int k=h; k<h+3;k++){
                            for(int m=w; m<w+3;m++){
                                if(v[k][m]==v[i][j])flag[k][m]=false;
                        }
                    }
                }
            }
        }
    }
    rep(i,9){
        rep(j,9){
            if(flag[i][j])cout<<" ";
            else cout<<"*";
            cout<<v[i][j];
        }
        cout<<endl;
    }
}
};

C++: #include<map>
#include<set>
#include<list>
#include<cmath>
#include<queue>
#include<stack>
#include<cstdio>
#include<string>
#include<vector>
#include<complex>
#include<cstdlib>
#include<cstring>
#include<numeric>
#include<sstream>
#include<iostream>
#include<algorithm>
#include<functional>

#define mp       make_pair
#define pb       push_back
#define all(x)   (x).begin(),(x).end()
#define rep(i,n) for(int i=0;i<(n);i++)

using namespace std;

typedef    long long          ll;
typedef    unsigned long long ull;
typedef    vector<bool>       vb;
typedef    vector<int>        vi;
typedef    vector<vb>         vvb;
typedef    vector<vi>         vvi;
typedef    pair<int,int>      pii;

const int INF=1<<29;
const double EPS=1e-9;

const int dx[]={1,0,-1,0},dy[]={0,-1,0,1};
int n;
int board[10][10];
int main(){
	cin>>n;
	int cc = 0;
	for(int k = 0;k< n;k++){
		bool flag[10][10];
		if(cc++ != 0) puts("");

		rep(i,10){
			rep(j,10){
				flag[i][j] = true;
			}
		}
		for(int y = 1;y <=9;y++){
			for(int x = 1;x <=9;x++){
				cin>>board[y][x];
			}
		}
		for(int y = 1; y<=9;y+=3){//3×3ブロックごとの判定
			for(int x = 1;x <=9;x+=3){
				int cnt[10]={0};
				rep(i,3){
					rep(j,3){
						cnt[board[y+i][x+j]]+=1;
					}
				}
				rep(i,3){
					rep(j,3){
						if(cnt[board[y+i][x+j]]!=1){
							flag[y+i][x+j] =false;
						}
					}
				}
			}
		}
		for(int y = 1;y <=9;y++){//横の判定
			int cnt[10]={0};
			for(int x = 1;x <=9;x++){
				cnt[board[y][x]]+=1;
			}
			for(int x = 1; x<=9;x++){
				if(cnt[board[y][x]]!=1){
					flag[y][x] =false;
				}
			}
		}
		for(int x = 1;x <=9;x++){
			int cnt[10]={0};
			for(int y =1;y <=9;y++){
				cnt[board[y][x]]++;
			}
			for(int y = 1;y <=9;y++){
				if(cnt[board[y][x]]!=1){
					flag[y][x] = false;
				}
			}
		}
		for(int i = 1;i <=9;i++){
			for(int j = 1;j <=9;j++){
				printf("%c%d",(flag[i][j]?' ':'*'),board[i][j]);
			}
			puts("");
		}
	}
	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 / 3) * 3 + l / 3][(j % 3) * 3 + l % 3 ] == p[j][k]) {
							a[(j / 3) * 3 + l / 3][(j % 3) * 3 + l % 3 ] = 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++: #include<cstdio>
using namespace std;
int main(){
  int n,m[9][9];
  char c[9][9];
  scanf("%d",&n);
  for(int i=0;i<n;i++){
    
    for(int j=0;j<9;j++){
      for(int k=0;k<9;k++){
	scanf("%d",&m[j][k]);
	c[j][k] = ' ';
      }
    }
    int dx[9] = {0,1,2,0,1,2,0,1,2};
    int dy[9] = {0,0,0,1,1,1,2,2,2};
    for(int l=0;l<9;l++){
      for(int j=0;j<8;j++){
	for(int k = j+1;k<9;k++){
	  if(m[l][j] == m[l][k]){
	    c[l][j] = '*';
	    c[l][k] = '*';
	  }
	  if(m[j][l] == m[k][l]){
	    c[j][l] = '*';
	    c[k][l] = '*';
	  }
	}
      }
    }
    
    for(int j=0;j<=6;j+=3){
      for(int k=0;k<=6;k+=3){
	for(int l=0;l<8;l++){
	  for(int o=l+1;o<9;o++){
	    if(m[j+ dy[l]][k+ dx[l]] == m[j+ dy[o]][k+ dx[o]]){
	      c[j+ dy[l]][k+ dx[l]] = '*';
	      c[j+ dy[o]][k+ dx[o]] = '*';
	    }
	  }
	}
      }
    }

    for(int j=0;j<9;j++){
      for(int k=0;k<9;k++){
	printf("%c%d",c[j][k],m[j][k]);
      }
      putchar('\n');
    }

  }
  return (0);
}