Swift – 第4页 – 柳婼の blog

[swift] LeetCode 283. Move Zeroes

Given an array nums, write a function to move all 0’s to the end of it while maintaining the relative order of the non-zero elements.

For example, given nums = [0, 1, 0, 3, 12], after calling your function, nums should be [1, 3, 12, 0, 0].

Note:
You must do this in-place without making a copy of the array.
Minimize the total number of operations.
Credits:
Special thanks to @jianchao.li.fighter for adding this problem and creating all test cases.

var j = 0
for i in 0..<nums.count {
    if nums[i] != 0 {
        nums[j] = nums[i]
        j += 1
    }
}
for i in j..<nums.count {
    nums[i] = 0
}

var j = 0

for i in 0..<nums.count {

if nums[i] != 0 {

nums[j] = nums[i]

j += 1

}

for i in j..<nums.count {

nums[i] = 0

}

[swift] LeetCode 238. Product of Array Except Self

Given an array of n integers where n > 1, nums, return an array output such that output[i] is equal to the product of all the elements of nums except nums[i].

Solve it without division and in O(n).

For example, given [1,2,3,4], return [24,12,8,6].

Follow up:
Could you solve it with constant space complexity? (Note: The output array does not count as extra space for the purpose of space complexity analysis.)

func productExceptSelf(_ nums: [Int]) -> [Int] {
    var res = Array(repeating: 1, count: nums.count)
    var i = 0, v = 1

    while i < nums.count-1 {
        res[i+1] = res[i] * nums[i]
        i += 1
    }

    i = nums.count-2
    while i >= 0 {
        v *= nums[i+1]
        res[i] *= v
        i -= 1
    }
    return res
}

func productExceptSelf(_ nums: [Int]) -> [Int] {

var res = Array(repeating: 1, count: nums.count)

var i = 0, v = 1

while i < nums.count-1 {

res[i+1] = res[i] * nums[i]

i += 1

}

i = nums.count-2

while i >= 0 {

v *= nums[i+1]

res[i] *= v

i -= 1

}

return res

}

[swift] LeetCode 234. Palindrome Linked List

Given a singly linked list, determine if it is a palindrome.

Follow up:
Could you do it in O(n) time and O(1) space?

func isPalindrome(_ head: ListNode?) -> Bool {
    var arr = Array(repeating: -1, count: 999999), p = head
    var i = 0, j = 0

    while let q = p {
        arr[i] = q.val
        p = q.next; i+=1
    }

    j = i-1; i = 0

    while i < j {
        if arr[i] != arr[j] { return false }
        i+=1; j -= 1
    }

    return true
}

func isPalindrome(_ head: ListNode?) -> Bool {

var arr = Array(repeating: -1, count: 999999), p = head

var i = 0, j = 0

while let q = p {

arr[i] = q.val

p = q.next; i+=1

}

j = i-1; i = 0

while i < j {

if arr[i] != arr[j] { return false }

i+=1; j -= 1

}

return true

}

[swift] LeetCode 215. Kth Largest Element in an Array

Find the kth largest element in an unsorted array. Note that it is the kth largest element in the sorted order, not the kth distinct element.

For example,
Given [3,2,1,5,6,4] and k = 2, return 5.

Note:
You may assume k is always valid, 1 ≤ k ≤ array’s length.

Credits:
Special thanks to @mithmatt for adding this problem and creating all test cases.

func findKthLargest(_ nums: [Int], _ k: Int) -> Int {
    if nums.isEmpty { return 0 }
    let sn = nums.sorted(by: >)
    return (k <= sn.count && k > 0) ? sn[k-1] : sn[0]
}

func findKthLargest(_ nums: [Int], _ k: Int) -> Int {

if nums.isEmpty { return 0 }

let sn = nums.sorted(by: >)

return (k <= sn.count && k > 0) ? sn[k-1] : sn[0]

}

[swift] LeetCode 206. Reverse Linked List

Reverse a singly linked list.

func reverseList(_ head: ListNode?) -> ListNode? {
    var stack = [Int](), p = head
    while let t = p {
        stack.append(t.val)
        p = t.next
    }
    p = head
    while let t = p {
        t.val = stack.popLast()!
        p = t.next
    }
    return head
}

func reverseList(_ head: ListNode?) -> ListNode? {

var stack = [Int](), p = head

while let t = p {

stack.append(t.val)

p = t.next

}

p = head

while let t = p {

t.val = stack.popLast()!

p = t.next

}

return head

}

[swift] LeetCode 198. House Robber

You are a professional robber planning to rob houses along a street. Each house has a certain amount of money stashed, the only constraint stopping you from robbing each of them is that adjacent houses have security system connected and it will automatically contact the police if two adjacent houses were broken into on the same night.

Given a list of non-negative integers representing the amount of money of each house, determine the maximum amount of money you can rob tonight without alerting the police.

Credits:
Special thanks to @ifanchu for adding this problem and creating all test cases. Also thanks to @ts for adding additional test cases.

func rob(_ nums: [Int]) -> Int {
    if nums.count < 1 { return nums.first ?? 0 }
    var lm = 0, gm = 0
    for i in 0..<nums.count {
        let t = lm
        lm = gm
        gm = max(gm, t + nums[i])
    }

    return gm
}

func rob(_ nums: [Int]) -> Int {

if nums.count < 1 { return nums.first ?? 0 }

var lm = 0, gm = 0

for i in 0..<nums.count {

let t = lm

lm = gm

gm = max(gm, t + nums[i])

}

return gm

}