//ARRAY PROBLEMS FOR COMS 161 – FRIDAY NOV 22nd 2019

//1(a) Display an array left-to-right

list = new Array(10, 20, 40, 50, 65, 89, 93);

i = 0;
N = list.length;

while (i < N) {
  alert(list[i]);
  i++;
}

//1(b) Display an array right-to-left??


i = list.length - 1;

while (i >= 0) {
   alert(list[i]);
   i--;
}


//2(a) Find the average of the array elements

i = 0;
N = list.length;
sum = 0;

while (i < N) {
   //what to put here??
   sum += list[i];
   i++;
}

//what to put down here??
alert("average = " + (sum/N));



//2(b) Find the average AND the median of the array elements
// The median is the middle number in a sorted array, 
// when there is just one middle number (i.e. when N is odd)
// but it is the average of the 2 middle numbers when N is even. 

if (N % 2 == 1)
  alert("median = " + list[(N-1)/2];
else {
  med = (list[N/2] + list[N/2 - 1])/ 2;
  alert("median = " + med);
}

 

//3 The Binary Search Algorithm for N = 7:

prez = new Array("Carter", "Clinton", "Eisenhower","Kennedy", "Nixon", "Obama", "Reagan");
year = new Array(1976,     1992,      1952,         1960,      1968,    2008,    1980);
termLength = new Array(4,    8,       8,           3,         6,       8,       8);

N = prez.length;
desired = prompt("Enter last name of desired president: ");
//Trace this mentally with Nixon

first = 0;  
last =  6;
found = false;


while (first <= last && found == false) {

      mid = (first + last)/2;     

      alert("first = " + first + "  last = " + last + "  mid = " + mid);

      if (desired > prez[mid])
           first = mid + 1;
      else if (desired < prez[mid])
           last = mid - 1;
      else
           found = true; 
}

 
if (found == true) {
  alert(desired + " was elected in " + year[mid]);
  alert("He served " + termLength[mid] + " years as President");
  alert("His term ran from " + year[mid] + " to " + (year[mid]+termLength[mid]));
}
else {
  alert("first = " + first + "  last = " + last);
  alert("Could not find " + desired);
}