longestCommonPrefix.js

/**
 * @param {string[]} strs
 * @return {string}
 */
var longestCommonPrefix = function(strs) {
  // initialize matches found map
  var matchesFound = {};
  var commonPrefix = '';
  var lastMatchedPrefix;
  var matchesFoundKeys;
  
  if (strs.length === 1) {
    return strs[0];
  }

  
  var findCommonPrefix = function(word1, word2) {
    var result = [];
    
    var a = word1.split('');
    var b = word2.split('');
    
    for(var i = 0, il = a.length; i < il; i++) {
      if (a[i] === b[i]) {
        result.push(a[i]);
      } else {
        break;
      }
    }
    
    return result.join('');
  };
  
  for (var i = 0, j = 1, il = strs.length; i < il && strs[j]; i++, j++) {
    lastMatchedPrefix = findCommonPrefix(strs[i], strs[j]);
    if (lastMatchedPrefix) {
      matchesFound[lastMatchedPrefix] = (matchesFound[lastMatchedPrefix] || 0) + 1;
    }
  }
  
  matchesFoundKeys = Object.keys(matchesFound);
  if (matchesFoundKeys.length <= strs.length - 1 && matchesFoundKeys.length > 1) {
    for (var i = 0, j = 1, il = matchesFoundKeys.length; i < il && matchesFoundKeys[j]; i++, j++) {
      commonPrefix = findCommonPrefix(matchesFoundKeys[i], matchesFoundKeys[j]);
    }
  } else if (matchesFoundKeys.length === 1) {
    commonPrefix = lastMatchedPrefix;
  }
  
  return commonPrefix;
  
  
  // iterate through each word in the str array
    // if a[i] === b[i] then add to result and keep checking
    // else break and move onto the next word
  // if matches found === strs.length - 1 && matches.found > 1
    // iterate again
  // return match or empty string
};