Write a program that generates a sequence of 20 random die tosses and that prints the die values, marking only the longest run

Question

import random
L = [random.randrange(1, 7) for i in range(20)]
print(L)

inRun = False

for i in range(len(L)):
    if inRun:
        if L[i] != L[i-1]:
            print (')', end = '')
            inRun = False
    if not inRun:
        if i != len(L)-1:
            if L[i] == L[i+1]:
                print('(', end = '')
                inRun = True
    print(L[i], end = '')

if inRun:
    print(')', end = '') 

Input list : [4, 5, 2, 6, 6, 5, 5, 5, 6, 2, 2, 1, 6, 5, 2, 1, 3, 3, 6, 3]

Output: 452(66)(555)6(22)16521(33)63
Should output : 45266(555)622165213363

I am having troubles marking the longest run rather than marking every number adjacent that is the same.

[edit]Thanks for the solutions everyone! To build on this code how can I return the indexes of the longest run?

Answer 1

The issue with your code is that you mark every run of numbers. I would suggest you run your loop then edit it with brackets. So before you mark every run you need to store all the runs and then pick the longest. I would recommend using a built-in function called sorted:

L = ["99", "888", "1"]
print(sorted(L, key=len))

Using the function we are able to track the longest run. Try the following code:

import random
L = [random.randrange(1, 7) for i in range(20)]
runs = []
print(L)

inRun = False

#count the run lenght
run = ""
for i in range(len(L)):
    if inRun:
        if L[i] != L[i-1]:
            # add the last run we have collected during the loop
            runs.append(run)



            # research for more runs
            run = ""
            inRun = False
            continue
        else:
            run += str(L[i])


    if not inRun:
        if i != len(L)-1:
            if L[i] == L[i+1]:
                run += str(L[i])

                inRun = True


print("\n")

#sort runs so the longest run is in index -1 (last)
# key=len means we sort by len

runs = sorted(runs, key=len)
# create a new string variable holding our list so we could use replace function
# we must use the string value of every int using str(x)
result = ""


if (len(runs) > 0):
    result = result.join(str(x) for x in L)

    #replacing the run with the same value but with "()"
    result = result.replace(runs[-1], "(" + runs[-1] + ")" , 1) # use 1 to tell python not mark more than one run if possible



print(result)

Please tell me if it solved your issue. All the best;

Answer 2

You are pretty close. The logic for your on/off switch for the grouping is not working quite right. Consider creating the subgroups and a variable that tracks the longest one seen. Then iterate of the subgroups and add parens around the one with the correct (longest) length.

import random

L = [random.randrange(1, 7) for i in range(20)]
groups = []
current_run = []
longest_run = 0
for x in L:
    if (not current_run) or (x == current_run[-1]):
        current_run.append(x)
        if longest_run < len(current_run):
            longest_run += 1
    else:
        groups.append(current_run)
        current_run = [x]

for g in groups:
    g_str = ''.join(map(str, g))
    if len(g) == longest_run:
        print(f'({g_str})', end='')
    else:
        print(g_str, end='')

For you example of L = [4, 5, 2, 6, 6, 5, 5, 5, 6, 2, 2, 1, 6, 5, 2, 1, 3, 3, 6, 3], you would see the following:

groups
# returns:
[[4],
 [5],
 [2],
 [6, 6],
 [5, 5, 5],
 [6],
 [2, 2],
 [1],
 [6],
 [5],
 [2],
 [1],
 [3, 3],
 [6]]

# printed output:
45266(555)62216521336