Language: C

#include<stdio.h>
int main()
{
        //field : ????????°??¬?????¶???
        //used : ???????????????????????????????????????????????°?????????????????????
	int field[10][10], used[10];
        //judge : ??°??¬???????????£???????????¨?????????true???
	bool judge[10][10];

	int num;
	cin >> num;
	while(num--)
	{
		memset(judge, false, sizeof(judge));

		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++)
		{
			memset(used, 0, sizeof(used));
			for(int j = 0; j < 9; j++)
			{
				used[field[i][j]]++;
			}
			for(int j = 1; j <=9; j++)
			{
				if(used[j] >= 2)
				{
					for(int k = 0; k < 9; k++)
					{
						if(field[i][k] == j)
						{
							judge[i][k] = true;
						}
					}
				}
			}
			memset(used, 0, sizeof(used));
			for(int j = 0; j < 9; j++)
			{
				used[field[j][i]]++;
			}
			for(int j = 1; j<= 9; j++)
			{
				if(used[j] >= 2)
				{
					for(int k = 0; k < 9; k++)
					{
						if(field[k][i] == j)
						{
							judge[k][i] = true;
						}
					}
				}
			}
		}

		for(int l = 0; l < 9; l+=3)
		{
			for(int m = 0; m < 9; m+=3)
			{
				memset(used, false, sizeof(used));
				for(int i = 0; i < 3; i++)
				{
					for(int j = 0; j < 3; j++)
					{
						used[field[i+l][j+m]]++;
					}
				}

				for(int n = 1; n <=9; n++)
				{
					if(used[n] >= 2)
					{
						for(int i = 0; i < 3; i++)
						{
							for(int j = 0; j < 3; j++)
							{
								if(field[i+l][j+m] == n)
								{
									judge[i+l][j+m] = true;
								}
							}
						}
					}
				}
			}
		}

		for(int i = 0; i < 9; i++)
		{
			for(int j = 0; j < 9; j++)
			{
				printf("%s%d",(judge[i][j])?"*":" " ,field[i][j]);
			}
			puts("");
		}
		if(num != 0)
		{
			puts("");
		}
	}
}

Compiler output:
main.c: In function 'main':
main.c:8:9: error: unknown type name 'bool'
    8 |         bool judge[10][10];
      |         ^~~~
main.c:2:1: note: 'bool' is defined in header '<stdbool.h>'; this is probably fixable by adding '#include <stdbool.h>'
    1 | #include<stdio.h>
  +++ |+#include <stdbool.h>
    2 | int main()
main.c:11:9: error: 'cin' undeclared (first use in this function)
   11 |         cin >> num;
      |         ^~~
main.c:11:9: note: each undeclared identifier is reported only once for each function it appears in
main.c:14:17: error: implicit declaration of function 'memset' [-Wimplicit-function-declaration]
   14 |                 memset(judge, false, sizeof(judge));
      |                 ^~~~~~
main.c:2:1: note: include '<string.h>' or provide a declaration of 'memset'
    1 | #include<stdio.h>
  +++ |+#include <string.h>
    2 | int main()
main.c:14:17: warning: incompatible implicit declaration of built-in function 'memset' [-Wbuiltin-declaration-mismatch]
   14 |                 memset(judge, false, sizeof(judge));
      |                 ^~~~~~
main.c:14:17: note: include '<string.h>' or provide a declaration of 'memset'
main.c:14:31: error: 'false' undeclared (first use in this function)
   14 |                 memset(judge, false, sizeof(judge));
      |                               ^~~~~
main.c:14:31: note: 'false' is defined in header '<stdbool.h>'; this is probably fixable by adding '#include <stdbool.h>'
main.c:38:71: error: 'true' undeclared (first use in this function)
   38 |                                                         judge[i][k] = true;
      |                                                                       ^~~~
main.c:38:71: note: 'true' is defined in header '<stdbool.h>'; this is probably fixable by adding '#include <stdbool.h>'