如何解决此错误文件“test.py”，第 5 行，在<module> for _ in range(b[0]): TypeError: 'int' object 不可订阅</module>

Question

I am trying to solve this problem:

Covid-19 is spreading fast! There are N cities, numbered from 0 to N−1 , arranged in a circular manner. City 0 is connected to city 1 , 1 to 2 , …, and city N−1 to city 0 .

The virus is currently at city X . Each day, it jumps from its current city, to the city K to its right, ie, from city X to the city (X+K)%N . As the virus jumps, the cities in between don't get infected. Cities once infected stay infected. You live in city Y . Find if it will reach your city eventually. If it will, print YES, else print NO.

The first line of the input consists of an integer T , the number of test cases.

The first and only line of each test case contains four space-separated integers - N , K , X and Y , denoting the number of cities, the size of jumps, Covid's current city, and the city that you live in, respectively.

This is the code I tried for it:

print("1- first write the number of times the program should run \n 2- write the of number of cities \n 3- size of jumps \n 4- virus current city \n 5- city you live in")

for _ in range(int(input())):
    a=[int(x) for x in input(). split()]
    for b in a:
        for _ in range(b[0]):
            b[2]=(b[2]+b[1])%b[0]
            if b[2]==b[3]:
                print("yes")
            else:
                print("NO")

Now I write this code as the first line will tell me how many times the code will run. Second line helps me to get the four values which will be different as to how many times the code will run that is a[0],a[1]..a[3] . and the third line will ittrate the first values of a into b .

But I am getting an error:

Traceback (most recent call last):
  File "covid.py", line 6, in <module>
    for _ in range(b[0]):
TypeError: 'int' object is not subscriptable

---

Example input:

2
6 2 5 3
12 3 4 2

Expected output:

YES
NO

Answer 1

Code is hard to read but i'll try my best to solve this: a is an integer, and integers can't be subscripted(basically accessed like an array eg. list[0], string[0:len(string)], tupl[0]) .

Answer 2

In your code, you have a defined as a list with values of integers. You are iterating through the list and trying to subscript the integer.

Let's take an example of the items you may enter as inputs: 10, 20, 30, ABCD, XYZ

You are expecting the below line of code to split the data into multiple elements. As you can see from the input, you have integers and strings. Your code will fail when it tries to process the list comprehension for a

a=[int(x) for x in input().split()]

Let's assume you entered all numeric values and also integers, say:

10 20 30 40 50

Now a will have [10, 20, 30, 40, 50]

Look at the next few lines of code:

for b in a:
    for _ in range(b[0]):
        b[2]=(b[2]+b[1])%b[0]
        if b[2]==b[3]:

What do you think is happening here? For the first iteration, b will have a value of 10. It is not a string and not a list. So the next line for _ in range(b[0]): will fail. Similarly, any reference of b[i] where i is an index of b will fail.

I have marked the lines that may be in error. Please review them.

a=[int(x) for x in input().split()]
for b in a:
    for _ in range(b[0]): #are you sure b is a list? this will fail
        b[2]=(b[2]+b[1])%b[0]. #you cannot do this as b is not a list
        if b[2]==b[3]: #same here, this will fail
            print("yes")
        else:
            print("NO")

Instead you can just use a and do everything you are trying to do within the loop for b in a: Instead of the entire section of the for loop, just add a line

b = (a[2]+a[1]) % a[0]

if b == a[3]:
    print("yes")
else:
    print("NO")

Answer 3

I am trying to solve this problem:

Covid-19 is spreading fast! There are N cities, numbered from 0 to N−1 , arranged in a circular manner. City 0 is connected to city 1 , 1 to 2 , …, and city N−1 to city 0 .

The virus is currently at city X . Each day, it jumps from its current city, to the city K to its right, ie, from city X to the city (X+K)%N . As the virus jumps, the cities in between don't get infected. Cities once infected stay infected. You live in city Y . Find if it will reach your city eventually. If it will, print YES, else print NO.

The first line of the input consists of an integer T , the number of test cases.

The first and only line of each test case contains four space-separated integers - N , K , X and Y , denoting the number of cities, the size of jumps, Covid's current city, and the city that you live in, respectively.

This is the code I tried for it:

print("1- first write the number of times the program should run \n 2- write the of number of cities \n 3- size of jumps \n 4- virus current city \n 5- city you live in")

for _ in range(int(input())):
    a=[int(x) for x in input(). split()]
    for b in a:
        for _ in range(b[0]):
            b[2]=(b[2]+b[1])%b[0]
            if b[2]==b[3]:
                print("yes")
            else:
                print("NO")

Now I write this code as the first line will tell me how many times the code will run. Second line helps me to get the four values which will be different as to how many times the code will run that is a[0],a[1]..a[3] . and the third line will ittrate the first values of a into b .

But I am getting an error:

Traceback (most recent call last):
  File "covid.py", line 6, in <module>
    for _ in range(b[0]):
TypeError: 'int' object is not subscriptable

---

Example input:

2
6 2 5 3
12 3 4 2

Expected output:

YES
NO