2D array diagonal checking loop

Question

I tried to create a 2D array and place four "X" in diagonal and created a double loop for detecting and counting the number of Xs ,it works but it doesnt do the job properly what it really does is that it counts the number of Xs in every row, my question how can i make it count just the Xs on diagonal ?

    var creatematrix = function (nbRang, nbColumn) {
        var result = Array(nbRang);
        for (var i=0; i<nbRang; i++) {
            result[i] = Array(nbColumn);
        }
        return result;
    };

    var m = creatematrix(6, 7);

for example if i did this

      m[4][1] = "X";
      m[3][2] = "X";
      m[2][3] = "X";
      m[1][4] = "X";

      m[5][3] = "O";
      m[3][3] = "O";
      m[4][3] = "O";
      m[2][4] = "O";

or this the result is the same

    m[1][1] = "X";
    m[2][1] = "X";
    m[3][1] = "X";
    m[4][1] = "X";



    m[5][3] = "O";
    m[3][3] = "O";
    m[4][3] = "O";
    m[2][4] = "O";

Here is what I have:

   var sumX = 0;
   for(var k = 5; k >= 0  ; k--){
       if(sumX == 4){
           alert("player 1 won");
       }
       for(var i = 0 ; i<= 6; i++){
           if(m[k][i]== "X" ){
               sumX += 1;
               break;
           }
           if(m[k][i]== "O" ){
              sumX = 0;         
           }
       }
   }

Ben McCormick · Accepted Answer · 2013-03-24 17:57:47Z

1

function getCount(m){
    var count =0;
    for(var i=0; i<m.length; i++)
    {
      if(m[i][m.length-i-1] === "X")
      {
         count++;
      }
    }

    return count;
}

That will just go down the diagonal and check each value.

You can also do a shorter (but less readable) version with

function getCount(m){
    return m.reduce(function(prev,current,index,arr){ 
      return prev + current[arr.length-index-1];},0);
}

JSFiddle

edited Mar 24, 2013 at 17:57

answered Mar 24, 2013 at 17:44

Ben McCormick

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6 Comments

Ben McCormick Over a year ago

@nooby102030 define "doesn't work" what doesn't it do that you expect?

mike10101 Over a year ago

your code doesnt count the X on the diagonal i tried it and it doesn't count them

Ben McCormick Over a year ago

I had a typo and it said counter instead of count. Thats fixed, and there's a working example here: jsfiddle.net/LknbJ

Ben McCormick Over a year ago

@nooby102030 which diagonal are you trying to count on? This code counts on the bottom left to top right diagonal, since that seemed like what you were trying for with your code. Is that what you want?

mike10101 Over a year ago

i saw the counter++ and i corrected it before you mention it but still doesnt do what i expect

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