你最后一种情况 i+j < n+1 枚举的时候应该是 g ++，手滑了吧

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

int n, i, j;

int main ()
{
	cin >> n >> i >> j;
	
	for ( int g = 1; g <= n; g ++)
	{
		printf ( "(%d,%d) ", i,g);
	}
	cout << '\n';
	for ( int g = 1; g <= n; g ++)
	{
		printf ( "(%d,%d) ", g, j);
	}
	cout << '\n';
	
	if ( i < j )
	for ( int g = 1; g <= n; g ++)
	{
		if ( j-i+g > n) break;
		else printf ( "(%d,%d) ",g,g+j-i);
	}
	else if ( i > j)
	for ( int g = 1; g <= n; g ++)
	{
		if ( i-j+g > n ) break;
		else printf ( "(%d,%d) " , i-j+g,g);
	}
	else 
	for ( int g = 1; g <= n; g ++)
	{
		printf ( "(%d,%d) ",g,g);
	}
	cout << '\n';

	
	if ( i + j > n+1)
	for ( int g = n; g >= 1; g --)
	{
		if ( i+j-g > n) break;
		else printf ( "(%d,%d) ",g,i+j-g);
	}
	else if ( i+j < n+1)
	for ( int g = 1; g <= n; g ++)
	{
		if (i+j-g < 1) break; 
		else printf ( "(%d,%d) ",i+j-g,g);
	}
	else //if ( i + j == n+1) 
	for ( int g = n; g >= 1; g --)
	{
		if ( n+1-g > n) break;
		else printf ( "(%d,%d) " ,g,n+1-g);
	}
	
	return 0;
}