```python
[Read More]
LC747. Largest Number At Least Twice of Others
two pass class Solution: def dominantIndex(self, A: List[int]) -> int: """ O(N)/O(1) 1. find largetst val and idx 2. compare with all other elements """ # two pass max_v = max_i = 0 for i in range(len(A)): if A[i] > max_v: max_v = A[i] max_i = i for a in...
[Read More]
LC561. Array Partition I
nums
class Solution:
def arrayPairSum(self, nums: List[int]) -> int:
nums.sort()
return sum(nums[::2])
LC448. Find All Numbers Disappeared in an Array
class Solution: def findDisappearedNumbers(self, nums: List[int]) -> List[int]: """ O(N)/O(1) two loops 1. iterate throught each num, mark nums[num-1] as negtive 2. loop through the array, the positions where numbers are positive is the missing numbers instead of using negtive sign to mark numbers at position i already existed, can...
[Read More]
LC268. Missing Number
```python
class Solution:
def missingNumber(self, A: List[int]) -> int:
“”” O(N) /O(1)
1. get expected sum if A is sequence
2. cnt actual sum
3. the one missing is difference
"""
n = len(A)
total = n*(n+1)//2
actual = sum(A)
return total - actual
[Read More]