Add new solution

Varun's TicTacToe Problem/Solutions/chen_solution.c

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+#include <stdio.h>
+#include <stdbool.h>
+#include <string.h>
+
+#define POSSIBLE_COMBS (19683)
+#define NUM_SQUARES (9)
+#define CLA_FLAG_COMPLETE ("-c")
+#define CLA_FLAG_PLAY ("-p")
+
+typedef unsigned char byte;
+
+enum ValidationState {
+ VALIDATE_NONE = 0,
+ VALIDATE_COMPLETE,
+ VALIDATE_PLAY
+};
+
+int multiplicity(byte board[NUM_SQUARES], int element);
+bool verifyBoard(byte board[NUM_SQUARES], enum ValidationState v);
+void outputBoard(byte board[NUM_SQUARES]);
+bool validWinningStates(byte board[NUM_SQUARES]);
+
+int main(int argc, char *argv[]) {
+ byte c[NUM_SQUARES] = {0};
+ int k = 0;
+ enum ValidationState v = VALIDATE_NONE;
+
+ if(argc > 1) {
+ if(!strcmp(argv[1], CLA_FLAG_COMPLETE)) { v = VALIDATE_COMPLETE; }
+ else if(!strcmp(argv[1], CLA_FLAG_PLAY)) { v = VALIDATE_PLAY; }
+ }
+
+ for(int i = 0, state = i; i < POSSIBLE_COMBS; i++, state = i) {
+ for(int j = 0; j < NUM_SQUARES; j++, state /= 3) {
+ c[j] = state % 3;
+ }
+
+ if(verifyBoard(c, v)) {
+ k++;
+ outputBoard(c); 
+ putc('\n', stdout);
+ }
+ } 
+ printf("[%d]\n", k);
+}
+
+int multiplicity(byte board[NUM_SQUARES], int element) {
+ int m = 0;
+ for(int i = 0; i < NUM_SQUARES; i++) { m += (board[i] == element); }
+ return m;
+}
+
+bool verifyBoard(byte board[NUM_SQUARES], enum ValidationState v) {
+ if(v == VALIDATE_NONE) { return true; }
+
+ int m1 = multiplicity(board, 1),
+ m2 = multiplicity(board, 2);
+
+ //Simple checks
+ //1. Number of Xs vs number of Os (difference must be one)
+ // --> 1 -> O, 2 -> X
+ if(m1 - m2 != 1 && m1 - m2 != 0) {
+ return false;
+ }
+
+ //For a complete board at least O or X should have a multiplicity that is a factor of 3
+ if(v == VALIDATE_COMPLETE) {
+ if(m1 % 3 != 0 || m2 % 3 != 0) { return false; }
+ }
+ //2. Only one winning pattern
+ if(!validWinningStates(board)) {
+ return false;
+ }
+
+ return true;
+}
+
+void outputBoard(byte board[NUM_SQUARES]) {
+ int spec = 0;
+ char c;
+ for(int i = 0; i < NUM_SQUARES; i++) {
+ spec = i % 3 == 2;
+
+ if(board[i] == 0) { c = ' '; }
+ else { c = board[i] == 1 ? 'O' : 'X'; }
+
+ printf(" %c %c", c, spec ? '\n' : '|');
+ if(spec && i != NUM_SQUARES - 1) {
+ printf("---+---+---\n");
+ }
+ }
+}
+
+bool validWinningStates(byte b[NUM_SQUARES]) {
+ int states = 0;
+ int board[NUM_SQUARES];
+ for(int i = 0; i < NUM_SQUARES; i++) { board[i] = b[i]; }
+
+ for(int i = 0, j = 0; i < NUM_SQUARES; i += 3, j /= 3) {
+ //Horizontal cases
+ if(board[i] == board[i+1] && board[i] == board[i+2] && board[i] != 0) {
+ board[i] = 0;
+ board[i + 1] = 0;
+ board[i + 2] = 0;
+ states += 1;
+ }
+
+ //Vertical cases
+ if(board[j] == board[j + 3] && board[i/3] == board[j + 6] && board[i] != 0) {
+ board[j] = 0;
+ board[j + 3] = 0;
+ board[j + 6] = 0;
+ states += 1;
+ } 
+ } 
+
+ //Seperately do diagonals
+ if(board[0] == board[4] && board[0] == board[8]) { states += 1; }
+ if(board[2] == board[4] && board[2] == board[6]) { states += 1; }
+
+ return states < 2;
+}
+