https://itemku.com/s/fetest

question1.js

//repl.it/repls/LimeWholeRedundancy

function solution(record) {
    var answer = [];
    var dbUser = {};

    for (var index in record) {
      var commands = record[index].split(' ');

      switch(commands[0]) {
        case 'Enter':
          answer.push(commands[1] + ' came in.');
          if (commands[2]) {
            dbUser[commands[1]] = commands[2];
          }
          break;
        case 'Leave':
          answer.push(commands[1] + ' has left.');
          break;
        case 'Change':
          if (commands[2]) {
            dbUser[commands[1]] = commands[2];
          }

      }
    }

    for (index in answer) {
      for (var userId in dbUser) {
        answer[index] = answer[index].replace(userId, dbUser[userId]);
      }
    }

    return answer;
}

console.log(solution(["Enter uid1234 Muzi", "Enter uid4567 Prodo", "Leave uid1234", "Enter uid1234 Prodo", "Change uid4567 Ryan"]))

question2.js

//repl.it/repls/RapidBigVisitors

function solution(N, users) {
    var answer = [];
    var keyValue = [];

    for(var i=1; i<=N; i++) {
      var numberOfFail = 0;
      var numberOfReached = 0;

      for(var index in users) {
        var stage = users[index];
        if (stage==i) {
          numberOfFail++;
        }
        if (stage>=i) {
          numberOfReached++;
        }
      }
      keyValue.push({key: i, val:numberOfFail/numberOfReached});
    }

    keyValue = keyValue.sort(function (a, b) {
        return a.val < b.val;
    });
    for(index in keyValue) {
      answer.push(keyValue[index].key);
    }
    return answer;
}

console.log(solution(5, [2,1,2,6,2,4,3,3]));

question3.js

//repl.it/repls/PhysicalMatureAdaware
function solution(relation) {
    var answer = 0;

    var combinations = [];
    // first combinations
    for (var row in relation) {
      var columns = relation[row];
      for (var i=0; i<columns.length; i++) {
        if (combinations[i]==undefined) {
          combinations[i] = {};
          combinations[i][columns[i]] = {};
          combinations[i][columns[i]] = 1;
        }
        else if (combinations[i][columns[i]]== undefined) {
          combinations[i][columns[i]] = 1;
        }
        else if (combinations[i][columns[i]]) {
            combinations[i] = false;
        }
      }
    }

    var tookColumns = [];
    for (row in combinations) {
      if (combinations[row]) {
        tookColumns[row] = 1;
        answer ++;
      } else {
        delete combinations[row];
      }
    }

    // second combinations
    combinations = {};
    for (var row in relation) {
      var columns = relation[row];
      for (var i=0; i<columns.length-1; i++) {
        if (tookColumns[i]) {
          continue;
        }

        for (var j=i+1; j<columns.length; j++) {
          if (tookColumns[j]) {
            continue;
          }

          if (combinations[i+'x'+j]==undefined) {
            combinations[i+'x'+j] = {};
            combinations[i+'x'+j][columns[i]] = {};
            combinations[i+'x'+j][columns[i]][columns[j]] = 1;
          } else if (combinations[i+'x'+j][columns[i]]==undefined) {
            combinations[i+'x'+j][columns[i]] = {};
            combinations[i+'x'+j][columns[i]][columns[j]] = 1;
          }
          else if (combinations[i+'x'+j][columns[i]][columns[j]]==undefined) {
            combinations[i+'x'+j][columns[i]][columns[j]] = 1;
          }
          else if (combinations[i+'x'+j][columns[i]] && combinations[i+'x'+j][columns[i]][columns[j]]) {
              combinations[i+'x'+j] = false;
          }

        }

      }
    }
    for (row in combinations) {
      if (combinations[row]) {
        answer ++;
      }
    }
    return answer;
}

console.log(solution([["100","ryan","music","2"],["200","apeach","math","2"],["300","tube","computer","3"],["400","con","computer","4"],["500","muzi","music","3"],["600","apeach","music","2"]]))