I am wondering why the following outputs (529, 23) rather than (484, 22)-CodePudding

for x in range(0,501):
    
    m = x ** 2
    if m > 500:
        break
        
print (m,x)
    
#this outputs a value for the highest square that is above 500 when I want the highest that is below 500

CodePudding user response：

The problem is you are breaking the loop once the value for m has already exceeded 500. So when you try to print the value for m it is the value that is above 500.

A solution would be to use the value of x and because we know that the desired value would be one less than this, we can compute m like so:

for x in range(501):
    m = x ** 2
    if m > 500:
        break

x -= 1
print(x**2, x)

CodePudding user response：

Yet another approach:

n = 0
for x in range(500):
    m, n = n, (x   1) ** 2
    if n > 500:
        break
        
print(m, x)  # 484 22

CodePudding user response：

Your code assigns the value of m before breaking, so it stores that value before breaking. Try this instead:

for x in range(0, 501):
    if (x   1) ** 2 > 500:
        m = x ** 2
        break
print(x, m)

Notes

Since you're new and it sounds like you're still learning about coding, I will add a few pointers.

First, you don't need to assign value to x to test the value of a function applied to it. Second, a better approach would be to use a while loop rather than a for loop, like this:

x = 0
while (x   1) ** 2 < 500:
    x = x   1
print(x, x**2)

Additionally, loops are slow, brute force ways to write code. Sometimes that's okay or necessary, but when there's a very efficient way to solve a problem without a loop, it's usually better to use it. For example, to find the smallest integer whose square is less than or equal to x, we can use:

import math
def int_root(x):
    return int(math.sqrt(x))
int_root(500)

CodePudding user response：

As mentioned by others the issue with your code is that when you check to see if m is greater than 500, if m is exceeding 500 the program breaks the loop, the catch is that m has already been given the value that is over 500 and as such prints that out instead of the desired one before. To counteract this we can add to x and square the result to see if that answer is over 500 and if it is the program will break.

def squareless(top):
    for x in range(0, top):
        if (x   1) ** 2 > top   1:
            m = x ** 2
            print(x, m)
            break
squareless(500)

CodePudding user response：

You break the loop after m already exceeds 500, so (529, 23) is expected. Note that 23 ** 2 = 529. You want to retreat to the previous x and previous m in this case.

for x in range(0,501):
    m = x ** 2
    if m > 500:
        x -= 1
        m = x ** 2
        break
        
print (m,x) # 484 22

Or check the next x to break before exceeding 500:

for x in range(0,501):
    m = x ** 2
    if (x 1) ** 2 > 500:
        break