Not letting letters repeat in a 5 by 5 table

[Goblue89]

I'm having problems figuring out how I get letters not to repeat. My whole plan is to create a 5 by 5 matrix and have entry[] fill it with the word Happiness and the Alphabet (excluding Z), but I can't have letters repeat I.E.

H A P I N
E S B C D
F G J K L
M O Q R T
U V W X Y

The plan is when H is placed in inside[] sets H to true and doesn't repeat it again in the table.

string entry[] = {"H", "A", "P", "P", "I", "N", "E", "S", "S", 
"A", "B", "C", "D", "E", "F", "G", "H", "I" "J", "K", "L", "M", 
"N", "O", "P", "Q", "R", "S", "T", "U", "V", "W", "X", "Y"};

bool value[25] = {false}; 

I'm confused on where to begin.