vinimdocarmo/node-peak-finding

'use strict';

var floor = Math.floor;

/**
 *
 * @param {Array} array - An array of number or a matrix (array of arrays)
 *
 * @returns {Number}
 */
module.exports = function peakFinding(array) {
    if(!Array.isArray(array)) {
        throw new TypeError('Expected an Array');
    }

    var twoDimension = Array.isArray(array[0]);

    var len = array.length,
        firstIndex = 0,
        lastIndex = len - 1,
        middleIndex = floor(len/2);

    while(firstIndex <= lastIndex) {
        var currEl, leftEl, rightEl;

        middleIndex = floor((firstIndex + lastIndex) / 2);

        if(twoDimension) {
            var max = array[0][middleIndex],
                rowIndex = 0;

            for(var i = 1; i < len; i++) {
                if(array[i][middleIndex] > max) {
                    max = array[i][middleIndex];
                    rowIndex = i;
                }
            }

            currEl  = array[rowIndex][middleIndex];
            leftEl  = array[rowIndex][middleIndex - 1];
            rightEl = array[rowIndex][middleIndex + 1];
        } else {
            currEl  = array[middleIndex];
            leftEl  = array[middleIndex - 1];
            rightEl = array[middleIndex + 1];
        }

        if(currEl < leftEl) {
            lastIndex = middleIndex - 1;
        } else if(currEl < rightEl) {
            firstIndex = middleIndex + 1;
        } else {
            return currEl;
        }
    }
};