basically I am attempting to make a a efficient/smallish C game of Tic-Tac-Toe. I have implemented everything other then the AI for the computer so far. my squares are basically structs in an array with an assigned value based on the square. For example
s[1].value = 1; therefore it's a x, and then a value of 3 would be a o. My question is whats the best way to create a semi-decent game playing AI for my tic-tac-toe game? I don't really want to use minimax, since It's not what I need. So how do I avoid a a lot of if statments and make it more efficient.
Here is the rest of my code:
#include <stdio.h> #include <stdlib.h> #include <string.h> #include <time.h> struct state{ // defined int state; // 0 is tie, 1 is user loss, 2 is user win, 3 is ongoing game int moves; }; struct square{ // one square of the board int value; // 1 is x, 3 is o char sign; // no space used }; struct square s[9]; //set up the struct struct state gamestate = {0,0}; //nothing void setUpGame(){ // setup the game int i = 0; for(i = 0; i < 9; i++){ s[i].value = 0; s[i].sign = ' '; } gamestate.moves=0; printf("\nHi user! You're \"x\"! I'm \"o\"! Good Luck :)\n"); } void displayBoard(){// displays the game board printf("\n %c | %c | %c\n", s[6].sign, s[7].sign, s[8].sign); printf("-----------\n"); printf(" %c | %c | %c\n", s[3].sign, s[4].sign, s[5].sign); printf("-----------\n"); printf(" %c | %c | %c\n\n", s[0].sign, s[1].sign, s[2].sign); } void getHumanMove(){ // get move from human int i; while(1){ printf(">>:"); char line[255]; // input the move to play fgets(line, sizeof(line), stdin); while(sscanf(line, "%d", &i) != 1) { //1 match of defined specifier on input line printf("Sorry, that's not a valid move!\n"); fgets(line, sizeof(line), stdin); } if(s[i-1].value != 0){printf("Sorry, That moves already been taken!\n\n");continue;} break; } s[i-1].value = 1; s[i-1].sign = 'x'; gamestate.moves++; } int sum(int x, int y, int z){return(x*y*z);} void getCompMove(){ // get the move from the computer } void checkWinner(){ // check the winner int i; for(i = 6; i < 9; i++){ // check cols if((sum(s[i].value,s[i-3].value,s[i-6].value)) == 8){printf("The Winner is o!\n");gamestate.state=1;} if((sum(s[i].value,s[i-3].value,s[i-6].value)) == 1){printf("The Winner is x!\n");gamestate.state=2;} } for(i = 0; i < 7; i+=3){ // check rows if((sum(s[i].value,s[i+1].value,s[i+2].value)) == 8){printf("The Winner is o!\n");gamestate.state=1;} if((sum(s[i].value,s[i+1].value,s[i+2].value)) == 1){printf("The Winner is x!\n");gamestate.state=2;} } if((sum(s[0].value,s[4].value,s[8].value)) == 8){printf("The Winner is o!\n");gamestate.state=1;} if((sum(s[0].value,s[4].value,s[8].value)) == 1){printf("The Winner is x!\n");gamestate.state=2;} if((sum(s[2].value,s[4].value,s[6].value)) == 8){printf("The Winner is o!\n");gamestate.state=1;} if((sum(s[2].value,s[4].value,s[6].value)) == 1){printf("The Winner is x!\n");gamestate.state=2;} } void playGame(){ // start playing the game gamestate.state = 3; //set-up the gamestate srand(time(NULL)); int temp = (rand()%2) + 1; if(temp == 2){ // if two comp goes first temp = (rand()%2) + 1; if(temp == 2){ s[4].value = 2; s[4].sign = 'o'; gamestate.moves++; }else{ s[2].value = 2; s[2].sign = 'o'; gamestate.moves++; } } displayBoard(); while(gamestate.state == 3){ if(gamestate.moves<10); getHumanMove(); if(gamestate.moves<10); getCompMove(); checkWinner(); if(gamestate.state == 3 && gamestate.moves==9){ printf("The game is a tie :p\n"); break; } displayBoard(); } } int main(int argc, const char *argv[]){ printf("Welcome to Tic Tac Toe\nby The Elite Noob\nEnter 1-9 To play a move, standard numpad\n1 is bottom-left, 9 is top-right\n"); while(1){ // while game is being played printf("\nPress 1 to play a new game, or any other number to exit;\n>>:"); char line[255]; // input whether or not to play the game fgets(line, sizeof(line), stdin); int choice; // user's choice about playing or not while(sscanf(line, "%d", &choice) != 1) { //1 match of defined specifier on input line printf("Sorry, that's not a valid option!\n"); fgets(line, sizeof(line), stdin); } if(choice == 1){ setUpGame(); // set's up the game playGame(); // Play a Game }else {break;} // exit the application } printf("\nThank's For playing!\nHave a good Day!\n"); return 0; } 
