Python Training date 21 jan

3sum.py

@@ -0,0 +1,34 @@
+def threeSum(nums):
+    nums.sort()
+    result = []
+    n = len(nums)
+
+    for i in range(n - 2):
+        # Skip duplicate values for i
+        if i > 0 and nums[i] == nums[i - 1]:
+            continue
+
+        left = i + 1
+        right = n - 1
+
+        while left < right:
+            total = nums[i] + nums[left] + nums[right]
+
+            if total == 0:
+                result.append([nums[i], nums[left], nums[right]])
+
+                # Skip duplicates for left and right
+                while left < right and nums[left] == nums[left + 1]:
+                    left += 1
+                while left < right and nums[right] == nums[right - 1]:
+                    right -= 1
+
+                left += 1
+                right -= 1
+
+            elif total < 0:
+                left += 1
+            else:
+                right -= 1
+
+    return result

4sum.py

@@ -0,0 +1,39 @@
+def fourSum(nums, target):
+    nums.sort()
+    n = len(nums)
+    result = []
+
+    for i in range(n - 3):
+        # Skip duplicates for first number
+        if i > 0 and nums[i] == nums[i - 1]:
+            continue
+
+        for j in range(i + 1, n - 2):
+            # Skip duplicates for second number
+            if j > i + 1 and nums[j] == nums[j - 1]:
+                continue
+
+            left = j + 1
+            right = n - 1
+
+            while left < right:
+                total = nums[i] + nums[j] + nums[left] + nums[right]
+
+                if total == target:
+                    result.append([nums[i], nums[j], nums[left], nums[right]])
+
+                    # Skip duplicates for left and right
+                    while left < right and nums[left] == nums[left + 1]:
+                        left += 1
+                    while left < right and nums[right] == nums[right - 1]:
+                        right -= 1
+
+                    left += 1
+                    right -= 1
+
+                elif total < target:
+                    left += 1
+                else:
+                    right -= 1
+
+    return result

Basic python code.py

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+#1. Print “Hello World”
+print("Hello World")
+
+
+#2. Sum of two numbers
+a = 10
+b = 20
+sum = a + b
+print("Sum =", sum)
+
+
+
+
+#3 Check whether a number is even or odd
+num = 7
+
+if num % 2 == 0:
+    print("Even")
+else:
+    print("Odd")
+
+
+
+
+#4 . Find the largest of two numbers
+a = 10
+b = 20
+
+if a > b:
+    print("Largest =", a)
+else:
+    print("Largest =", b)
+
+
+
+#5 Print numbers from 1 to 10
+for i in range(1, 11):
+    print(i)
+
+
+
+#6 Find factorial of a number
+num = 5
+fact = 1
+
+for i in range(1, num + 1):
+    fact = fact * i
+
+print("Factorial =", fact)
+
+
+
+#7 check whether a number is prime
+num = 7
+flag = True
+
+if num <= 1:
+    flag = False
+
+for i in range(2, num):
+    if num % i == 0:
+        flag = False
+        break
+
+if flag:
+    print("Prime number")
+else:
+    print("Not a prime number")
+
+
+
+
+#8 Reverse a string
+s = "python"
+rev = ""
+
+for ch in s:
+    rev = ch + rev
+
+print("Reversed string =", rev)
+
+
+
+#9 s = "python"
+rev = ""
+
+for ch in s:
+    rev = ch + rev
+
+print("Reversed string =", rev)
+
+
+
+#10. Find sum of elements in a list
+list1 = [1, 2, 3, 4, 5]
+total = 0
+
+for i in list1:
+    total += i
+
+print("Sum =", total)
+
+
+
+#11. Function to add two numbers
+def add(a, b):
+    return a + b
+
+print(add(5, 3))
+
+
+
+
+#12 Check even/odd using function
+def check_even_odd(num):
+    if num % 2 == 0:
+        return "Even"
+    else:
+        return "Odd"
+
+
+
+
+
+

Boyer–Moore Voting Algorithm.py

@@ -0,0 +1,26 @@
+def majorityElement(nums):
+    # Step 1: Find potential candidates
+    count1 = count2 = 0
+    candidate1 = candidate2 = None
+
+    for num in nums:
+        if num == candidate1:
+            count1 += 1
+        elif num == candidate2:
+            count2 += 1
+        elif count1 == 0:
+            candidate1, count1 = num, 1
+        elif count2 == 0:
+            candidate2, count2 = num, 1
+        else:
+            count1 -= 1
+            count2 -= 1
+
+    # Step 2: Verify the candidates
+    result = []
+    if nums.count(candidate1) > len(nums) // 3:
+        result.append(candidate1)
+    if candidate2 != candidate1 and nums.count(candidate2) > len(nums) // 3:
+        result.append(candidate2)
+
+    return result

First Unique Character in a String.py

@@ -0,0 +1,11 @@
+def firstUniqChar(s):
+    freq = {}
+
+    for ch in s:
+        freq[ch] = freq.get(ch, 0) + 1
+
+    for i, ch in enumerate(s):
+        if freq[ch] == 1:
+            return i
+
+    return -1

Range Sum Query – Immutable.py

@@ -0,0 +1,9 @@
+class NumArray:
+
+    def __init__(self, nums):
+        self.prefix = [0]
+        for num in nums:
+            self.prefix.append(self.prefix[-1] + num)
+
+    def sumRange(self, left, right):
+        return self.prefix[right + 1] - self.prefix[left]

Range Sum Query.py

@@ -0,0 +1,31 @@
+class NumArray:
+
+    def __init__(self, nums):
+        self.prefix = [0]
+        for num in nums:
+            self.prefix.append(self.prefix[-1] + num)
+
+    def sumRange(self, left: int, right: int) -> int:
+        return self.prefix[right + 1] - self.prefix[left]
+
+
+
+
+
+
+#Binary Search
+class Solution:
+    def search(self, nums, target):
+        left, right = 0, len(nums) - 1
+
+        while left <= right:
+            mid = (left + right) // 2
+
+            if nums[mid] == target:
+                return mid
+            elif nums[mid] < target:
+                left = mid + 1
+            else:
+                right = mid - 1
+
+        return -1

add binary.py

@@ -0,0 +1,20 @@
+class Solution:
+    def addBinary(self, a: str, b: str) -> str:
+        i, j = len(a) - 1, len(b) - 1
+        carry = 0
+        result = []
+
+        while i >= 0 or j >= 0 or carry:
+            total = carry
+
+            if i >= 0:
+                total += int(a[i])
+                i -= 1
+            if j >= 0:
+                total += int(b[j])
+                j -= 1
+
+            result.append(str(total % 2))
+            carry = total // 2
+
+        return ''.join(reversed(result))