Start to Use Python to Solve Algorithm Problems

Basic functions

For

a = ["hello", 1, 0.5]
for i, v in enumerate(a):
    print(i, v)

Output:

0 hello
1 1
2 0.5

---

While

while True:
    try:
        n = int(input())
        ...
    except EOFError:
        break

---

Operations

x = 5 #101(Base2)
y = 3 #011(Base2)
print(x + y, x - y, x * y, x / y)
print(x ** y, x // y, x % y)
print(x & y, x | y, x ^ y, x << y, x >> y)

Output:

8 2 15 1.6666666666666667
125 1 2
1 7 6 40 0

---

Min Max

a, b, c = 1, 3, 2
mn = min(a, b, c)
mx = max(a, b, c)
print(mn, mx)

Output

1 3

---

Numerical Base

x = int("144", 8)
a, b, c, d = bin(x), oct(x), int(x), hex(x)
print(a, b, c, d)
print(a[2:])
print(b[2:])
print(c)
print(d[2:])

Output:

0b1100100 0o144 100 0x64
1100100
144
100
64

Basic Types and Useful Types

String

Escape Character

\'      Single Quote
\\	    Backslash	
\n	    New Line	
\r	    Carriage Return
\t      Tab

s = '\# \' \\ """'
print(s)

Output:

# ' \ """

---

String Cut

v = 12345
s = str(v)
print(s[1:], s[2:3], s[:-1], s[-2], s[::2], s[::-1])

Output:

2345 3 1234 4 135 54321

---

String Internal Methods

link

List

l = ["hello", 1, [2, 3]]
la = [2, 1, 0, -1, -2]
lb = ["apple", "banana", "orange"]
la.sort()
lb.sort(reverse=True)
print(la)
print(lb)

Output:

[-2, -1, 0, 1, 2]
['orange', 'banana', 'apple']

---

queue.PriorityQueue

from queue import PriorityQueue
q = PriorityQueue()

q.put((2, "eat"))
q.put((1, "get up"))
q.put((3, "sleep"))

while not q.empty():
    next_item = q.get()
    print(next_item)

---

Array (Numpy)

import numpy as np
n, m = 2, 3
a = np.zeros((n, m), dtype=int)
print(type(a))
print(a)

---

Output:

<class 'numpy.ndarray'>
[ [0 0 0]
&emsp;[0 0 0] ]

Class

class A:
    def __init__(self, cnt, chr):
        self.cnt = cnt
        self.chr = chr
    def __lt__(self, other):
        if self.cnt != other.cnt:
            return self.cnt > other.cnt
        else:
            return self.chr < other.chr
    def __str__(self):
        return str(self.cnt) + " " + str(self.chr)

a = []
a.append(A(1, "apple"))
a.append(A(2, "banana"))
a.sort()
for i in range(len(a)):
    print(a[i])

Output:

2 banana
1 apple

---

Input

String

s = input()
print(type(s))
sa, sb = input().split(maxsplit=1)

Output:

<class 'str'>

---

List

l = []
print(type(l))
l = list(map(int, input().split()))
l2 = [[] for i in range(10000)] # = cpp l2 = list[10000]
lm = [[[0 for i in range(3)] for j in range(4)] for k in range(5)]
print(lm[4][3][2])

Output:

<class 'list'>
0

---

Dict

d = {}
print(type(d))

Output:

<class 'dict'>

---

Int

n, m = map(int, input().split())
print(type(n))

Output:

<class 'int'>

---

Output

One line

n = 5
a = []
for i in range(n):
    a.append(i*i)
for i in range(n):
    print(a[i],end=" " if i != n - 1 else "")
print()

Output:

0 1 4 9 16