Match sequential values of 2 lists-CodePudding

I would like to match sequential value pairs from 2 lists, a and b, and delete values from b list, keep only first larger value for b (compared to a) at same index position as a. lets look at a simple example

a = [206, 252, 272, 315, 349, 374, 394, 406, 440, 466]
b = [209, 220, 244, 255, 285, 301, 327, 358, 380, 396, 419, 447, 476, 492]

start by looking at value at index 0 in list a if b value at index 0 is smaller it shall be removed from b next look at index 1 in b , if smaller than a[0] it shall also be removed and so on...

final result should be :

b = [209,255,285,327,358,380,396,419,447,476]

my idea is to try a nested for loop

for idx, j in enumerate(a):
    for jdx, k in enumerate(b):
        if b[jdx] < a[idx]:
           del b[jdx]

However, I can not get the final result I want...

CodePudding user response：

Your code is close, but it doesn't move to the next value in list a like you want. This code gives the intended result:

a = [206, 252, 272, 315, 349, 374, 394, 406, 440, 466]
b = [209, 220, 244, 255, 285, 301, 327, 358, 380, 396, 419, 447, 476, 492]
output = []
for idx, j in enumerate(a):
    for jdx, k in enumerate(b):
        if b[jdx] >= a[idx]:
            output.append(b[jdx])
            break
print(output)

Output:

[209, 255, 285, 327, 358, 380, 396, 419, 447, 476]

CodePudding user response：

I think this is an acceptable solution:

a = [206, 252, 272, 315, 349, 374, 394, 406, 440, 466]
b = [209, 220, 244, 255, 285, 301, 327, 358, 380, 396, 419, 447, 476, 492]

result = []

try:
    a_iter = iter(a)
    b_iter = iter(b)
    a_value = next(a_iter)
    b_value = next(b_iter)
    while True:

        if a_value < b_value:
            result.append(b_value)
            a_value = next(a_iter)
            b_value = next(b_iter)
        else:
            b_value = next(b_iter)

except StopIteration:
    print(result)

CodePudding user response：

Simple and efficient solution, go to the next index as soon as b[i] has become larger than a[i]:

i = 0
n = len(a)
for b[i] in b:
    if i < n and b[i] > a[i]:
        i  = 1
del b[i:]

Or with a sentinel:

i = 0
a  = b[-1:]
for b[i] in b:
    if b[i] > a[i]:
        i  = 1
del b[i:]