C :

#include<stdio.h>
#include<string.h>
int main()
{
	int n,i,j,l[10];
	char x[10][51];
	scanf("%d",&n);
	getchar();
	for(i=0;i<n;i++)
	{
		gets(x[i]);
		l[i]=strlen(x[i]);
	}
	for(i=0;i<n;i++)
	{
		for(j=0;j<l[i];j++)
		{
			if(x[i][j]=='a'||x[i][j]=='e'||x[i][j]=='i'||x[i][j]=='o'||x[i][j]=='u')
			x[i][j]=x[i][j]-32;
			else	if(x[i][j]!='A'&&x[i][j]!='E'&&x[i][j]!='I'&&x[i][j]!='O'&&x[i][j]!='U'&&x[i][j]>='A'&&x[i][j]<='Z')
			x[i][j]=x[i][j]+32; 
		}
		x[i][j]='\0';
	}
	for(i=0;i<n;i++)
	{
		printf("%s",x[i]);
		if(i!=n-1)
		printf("\n");
	}
	
}

C++ :

#include<stdio.h>

#include<string.h>

#define N 50

int main()

{

	int i,j,T,counter=0;

	char a;

	char string[N];

	scanf("%d",&T);

	getchar();

	for(i=1;i<=T;i++)
	{
		gets(string);
		for(j=0;string[j]!='\0';j++)
		{
			if(string[j]>='A'&&string[j]<='Z')
			string[j]+=32;
			if(string[j]=='a'||string[j]=='e'||string[j]=='i'||string[j]=='o'||string[j]=='u')
			string[j]-=32;
			
		}
		printf("%s\n",string);
	}
}