[leogrr]

def ternary_search(seq,key):
    length=len(seq)
    left=0
    right=length
    index=0
    x=True
    while x and left<=right:
        if left==right:
            return index
    #once you know left==right,check and see if the value==key and if so then return either the left or right as both must be the index of that value
           
        else:
            if right-left>0:
                index1 = ((right+2*(left))//3)
                index2 = ((2*(right)+left)//3)
                if left == right:
                    x = False
                    return (index1+index2)
                if seq[index1] == key:
                    x = False
                    return index1
                if seq[index2]== key:
                    x = False
                    return index2
                if key<seq[index1]:
                    right = index1-1
                else:
                    if key > seq[index1] and key <seq[index2]:
                        right = index2-1
                        left = index1-1
                    if key > seq[index2]:
                        left = index2+1
    
    return index

def test():
    seq = []
    for i in range(1,1001):
        seq.append(i)
    for j in range(1,1001):
        is_pass = (ternary_search(seq,j)==j-1)
        assert is_pass == True, "fail the test when key is %d"%j
    if is_pass == True:
        print("=========== Congratulations! Your have finished exercise 2! ============")
if __name__ == '__main__':
    test()

I have this program, and I know where the error is occurring, and I left an idea of what I think should be done to fix it, but its still not working can someone please help me.

[Mekire]

Not sure if you are still stuck on this or not but you haven't gotten any response so here goes.

I think one of your main problems is you are doing integer division. You can't zero in on a value when it is nearby this way.

The following is a print out of (key,left,right) on my implementation searching for 500 (which is at index 499) but using integer division:

Spoiler

(500, 0, 666)
(500, 222, 666)
(500, 370, 666)
(500, 370, 567)
(500, 435, 567)
(500, 435, 523)
(500, 464, 523)
(500, 483, 523)
(500, 483, 509)
(500, 491, 509)
(500, 491, 503)
(500, 495, 503)
(500, 497, 503)
(500, 497, 501)
(500, 498, 501)
(500, 498, 500)
(500, 498, 500)
(500, 498, 500)
(500, 498, 500)

Notice how once we get close we don't get any closer.

You have to use true(floating point) division:

Spoiler

(500, 0, 666.0)
(500, 222.0, 666.0)
(500, 370.0, 666.0)
(500, 370.0, 567.3333333333334)
(500, 435.7777777777778, 567.3333333333334)
(500, 435.7777777777778, 523.4814814814815)
(500, 465.0123456790124, 523.4814814814815)
(500, 484.50205761316874, 523.4814814814815)
(500, 484.50205761316874, 510.48834019204395)
(500, 493.16415180612717, 510.48834019204395)
(500, 493.16415180612717, 504.71361073007165)
(500, 497.013971447442, 504.71361073007165)
(500, 497.013971447442, 502.1470643025284)
(500, 497.013971447442, 500.43603335083293)
(500, 498.1546587485723, 500.43603335083293)
(500, 498.91511694932586, 500.43603335083293)
(500, 498.91511694932586, 499.92906121699724)
(500, 498.91511694932586, 499.5910797944401)
(500, 498.91511694932586, 499.3657588460687)

This of course then requires that you compare rounds of the numbers (or use a precision tolerance) and index with there int equivalents.

You also seem to be over thinking the problem in general. you are using a ton of variables where you only really need 6 (including the arguments passed in).

• Check if left and right are equal (or close enough)
  
• if not, calculate your thirds.
  
• Determine which one moving would eliminate the largest part of the seq.
  
• Repeat.

Something like that.

Try some stuff and post back,
-Mek