//////////////////////////////////////////////////

// SOLUTION CODE

//////////////////////////////////////////////////

// To visualize, copy code into chrome console

//////////////////////////////////////////////////

// Optimal Meeting Point Algorithm:

//

// O(n) solution - iterate over the entire matrix - when we encounter

// people, we keep a running median of the row and col.

// At the end of the matrix, we return out the median row, and the median col

//

var getOptimalMeetingPoint = function (matrix) {

// init runningRow and runningCol and peopleCount

var runningRow = 0;

var runningCol = 0;

var peopleCount = 0;

for (var row = 0; row < matrix.length; row++) {

for (var col = 0; col < matrix[0].length; col++) {

// if there are people on the corner

if (matrix[row][col] !== 0) {

// add row * number of people on that corner

runningRow += row * matrix[row][col];

// add col * number of people on that corner

runningCol += col * matrix[row][col];

// add number of people to the running peopleCount

peopleCount += matrix[row][col];

}

}

}

// calculate the position in the matrix

matrix[Math.round(runningRow / peopleCount)][Math.round(runningCol / peopleCount)] = 'X';

return matrix;

};

//////////////////////////////////////////////////

// TEST CASES

//////////////////////////////////////////////////

range(10, 0).map(function () {

return buildMatrix(9, 15);

}).forEach(function (matrix) {

console.table(getOptimalMeetingPoint(matrix));

});

//////////////////////////////////////////////////

// MATRIX BUILDER

//////////////////////////////////////////////////

// Returns an array of rowSize length, populated with elm

function range (rowSize, elm) {

var result = [];

for (var i = 0; i < rowSize; i++) {

if (Array.isArray(elm)) {

result.push(elm.slice());

} else {

result.push(elm);

}

}

return result;

}

// randomize takes a matrix, it's size, number of random elms and elms

function randomize (matrix, size, num) {

if (num === 0) {

return matrix;

} else if (num > size * size) {

return "Number exceeds size of matrix";

}

// generate random row and col

var row = Math.floor(Math.random() * (size - 1));

var col = Math.floor(Math.random() * (size - 1));

// generate random number of citizens on square

var elm = Math.floor(Math.random() * 5);

// If we haven't placed a person at that coord, set a person on that coord,

// decrement num, then recurse up.

if (matrix[row][col] !== 0) {

return randomize(matrix.slice(), size, num);

} else {

matrix[row][col] = elm;

return randomize(matrix.slice(), size, num - 1);

}

};

// builds 2d array where num is the number of random pieces on the board

function buildMatrix (size, num) {

return randomize(range(size, range(size, 0)).slice(), size, num);

};