Question 90

Question

Please write a program which count and print the numbers of each character in a string input by console.

Example: If the following string is given as input to the program:

1abcdefgabc

Then, the output of the program should be:

1a,2
2c,2
3b,2
4e,1
5d,1
6g,1
7f,1

Hints

Use dict to store key/value pairs. Use dict.get() method to lookup a key with default value.

Main author's Solution: Python 2

1dic = {}
2s=raw_input()
3for s in s:
4    dic[s] = dic.get(s,0)+1
5print '\n'.join(['%s,%s' % (k, v) for k, v in dic.items()])

My Solution: Python 3

1import string
2
3s = input()
4for letter in string.ascii_lowercase:
5    cnt = s.count(letter)
6    if cnt > 0:
7        print("{},{}".format(letter,cnt))

OR

1s = input()
2for letter in range(ord('a'),ord('z')+1):    # ord() gets the ascii value of a char
3    letter = chr(letter)                     # chr() gets the char of an ascii value
4    cnt = s.count(letter)
5    if cnt > 0:
6        print("{},{}".format(letter,cnt))

Question 91

Question

Please write a program which accepts a string from console and print it in reverse order.

Example: If the following string is given as input to the program:*

1rise to vote sir

Then, the output of the program should be:

1ris etov ot esir

Hints

Use list[::-1] to iterate a list in a reverse order.

Main author's Solution: Python 2

1s=raw_input()
2s = s[::-1]
3print s

My Solution: Python 3

1s = input()
2s = ''.join(reversed(s))
3print(s)

Question 92

Question

Please write a program which accepts a string from console and print the characters that have even indexes.

Example: If the following string is given as input to the program:

1H1e2l3l4o5w6o7r8l9d

Then, the output of the program should be:

1Helloworld

Hints

Use list[::2] to iterate a list by step 2.

Main author's Solution: Python 2

1s=raw_input()
2s = s[::2]
3print s

My Solution: Python 3

1s = "H1e2l3l4o5w6o7r8l9d"
2s = [ s[i] for i in range(len(s)) if i%2 ==0 ]
3print(''.join(s))

OR

1s = "H1e2l3l4o5w6o7r8l9d"
2ns =''
3for i in range(len(s)):
4    if i % 2 == 0:
5        ns+=s[i]
6print(ns)

Question 93

Question

Please write a program which prints all permutations of [1,2,3]

Hints

Use itertools.permutations() to get permutations of list.

Solution:

1
2import itertools
3print list(itertools.permutations([1,2,3]))

Question 94

Question

Write a program to solve a classic ancient Chinese puzzle: We count 35 heads and 94 legs among the chickens and rabbits in a farm. How many rabbits and how many chickens do we have?

Hints

Use for loop to iterate all possible solutions.

Solution:

 1def solve(numheads,numlegs):
 2    ns='No solutions!'
 3    for i in range(numheads+1):
 4        j=numheads-i
 5        if 2*i+4*j==numlegs:
 6            return i,j
 7    return ns,ns
 8
 9numheads=35
10numlegs=94
11solutions=solve(numheads,numlegs)
12print solutions

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