{"id":4095,"date":"2020-05-01T00:01:14","date_gmt":"2020-05-01T07:01:14","guid":{"rendered":"https:\/\/c-for-dummies.com\/blog\/?p=4095"},"modified":"2020-05-08T08:23:13","modified_gmt":"2020-05-08T15:23:13","slug":"tic-tac-toe-evaluation","status":"publish","type":"post","link":"https:\/\/c-for-dummies.com\/blog\/?p=4095","title":{"rendered":"Tic-Tac-Toe Evaluation"},"content":{"rendered":"

This month’s Exercise may seem like a repeat of the Exercise “We Have a Winnah!”<\/a> from July of 2013. It’s not.
\n
\nThe July 2013 Exercise involved solving a tic-tac-toe like grid. Alas, the grid was filled with ones and zeros and only one grid pattern was presented. In a true game of tic-tac-toe, three characters occupy the grid: X, O, and blank. Further, multiple possibilities must be tested to assure a victory, which is why I’m presenting this, updated challenge.<\/p>\n

For this month’s Exercise, your task is to determine whether a completed and valid tic-tac-toe game grid holds a winning combination, which is three Xs or three Os across, down, or diagonal. To help meet this goal, I’ve provided a program skeleton available below as well as on GitHub<\/a>.<\/p>\n

Something I learned while researching this project is that you can’t randomly pack an array and expect it to represent realistic game play. Therefore, each string in the game[]<\/code> array represents a valid 3-by-3 game grid as a string of x, o, and space characters:<\/p>\n

char *game[6] = {
\n    \"xxoooxxox\",
\n    \"o x xox \",
\n    \"xx oxxooo\",
\n    \"o xooox x\",
\n    \" xo ox o\",
\n    \"x oxo xox\"
\n};
\n<\/code><\/p>\n

Each string lays out as rows and columns: \"xxoooxxox\"<\/code> stands for the completed game shown in Figure 1.<\/p>\n

\"sample

Figure 1. A sample game grid, no winner.<\/p><\/div>\n

The six strings in the array represent various possible solutions to a game of tic-tac-toe, along with some cat’s games (no winner). The code skeleton provided below contains the game[]<\/code> array, the output_grid()<\/em> function to display the array as a tic-tac-toe game, but the code is missing the is_winner()<\/em> function that evaluates each string for a winner and returns the winning token character.<\/p>\n

\r\n#include <stdio.h>\r\n\r\n\/* generate the tic-tac-toe grid *\/<\/span>\r\nvoid output_grid( char *g )\r\n{\r\n    int row;\r\n\r\n    for( row=0; row<3; row++)\r\n    {\r\n        printf(\" %c %c %c\\n\",\r\n                *(g+(3*row)),\r\n                *(g+(3*row)+1),\r\n                *(g+(3*row)+2)\r\n              );\r\n    }\r\n}\r\n\r\n\/* determine whether the game was won *\/<\/span>\r\nchar is_winner( char *g )\r\n{\r\n    return(' ');\r\n}\r\n\r\nint main()\r\n{\r\n    char *game[6] = {\r\n        \"xxoooxxox\",\r\n        \"o x xox  \",\r\n        \"xx oxxooo\",\r\n        \"o xooox x\",\r\n        \" xo ox  o\",\r\n        \"x oxo xox\"\r\n    };\r\n    int x,r;\r\n\r\n    \/* examine all five game results *\/<\/span>\r\n    for( x=0; x<6; x++ )\r\n    {\r\n        output_grid( game[x] );\r\n        printf(\"Game %d: \",x+1);\r\n        r = is_winner( game[x] );\r\n        switch(r)\r\n        {\r\n            case ' ':\r\n                puts(\"No winner\\n\");\r\n                break;\r\n            case 'x':\r\n                puts(\"X wins!\\n\");\r\n                break;\r\n            case 'o':\r\n                puts(\"O wins!\\n\");\r\n                break;\r\n            default:\r\n                puts(\"Unknown value\\n\");\r\n        }\r\n    }\r\n\r\n    return(0);\r\n}<\/pre>\n
Determine whether a given matrix wins a game of tic-tac-toe. Continue reading →<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[3],"tags":[],"class_list":["post-4095","post","type-post","status-publish","format-standard","hentry","category-exercise"],"_links":{"self":[{"href":"https:\/\/c-for-dummies.com\/blog\/index.php?rest_route=\/wp\/v2\/posts\/4095","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/c-for-dummies.com\/blog\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/c-for-dummies.com\/blog\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/c-for-dummies.com\/blog\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/c-for-dummies.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=4095"}],"version-history":[{"count":7,"href":"https:\/\/c-for-dummies.com\/blog\/index.php?rest_route=\/wp\/v2\/posts\/4095\/revisions"}],"predecessor-version":[{"id":4135,"href":"https:\/\/c-for-dummies.com\/blog\/index.php?rest_route=\/wp\/v2\/posts\/4095\/revisions\/4135"}],"wp:attachment":[{"href":"https:\/\/c-for-dummies.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=4095"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/c-for-dummies.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=4095"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/c-for-dummies.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=4095"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}
Your task for the Exercise is to code the is_winner()<\/em> function. Ensure that it evaluates all possible solutions and returns the winning token character, ‘x’ or ‘o’, or ‘ ‘ (space) for no winner. Click here<\/a> to view my solution.<\/p>\n","protected":false},"excerpt":{"rendered":"