Given an array containing n distinct numbers taken from 0, 1, 2, ..., n
, find the one that is missing from the array.
Example 1:
Input: [3,0,1] Output: 2
Example 2:
Input: [9,6,4,2,3,5,7,0,1] Output: 8
Note:
Your algorithm should run in linear runtime complexity. Could you implement it using only constant extra space complexity?
给定一个包含 0, 1, 2, ..., n
中 n 个数的序列,找出 0 .. n 中没有出现在序列中的那个数。
示例 1:
输入: [3,0,1] 输出: 2
示例 2:
输入: [9,6,4,2,3,5,7,0,1] 输出: 8
说明:
你的算法应具有线性时间复杂度。你能否仅使用额外常数空间来实现?
1 class Solution { 2 func missingNumber(_ nums: [Int]) -> Int { 3 //利用异或运算,将数组全体内容与0~n进行异或, 4 //根据异或运算的性质可知最后结果为缺少的那个数字。 5 var result:Int = nums.count 6 for i in 0..<nums.count 7 { 8 result ^= i ^ nums[i] 9 } 10 return result 11 } 12 }
28ms
1 class Solution { 2 func missingNumber(_ nums: [Int]) -> Int { 3 var h = (nums.count+1)*nums.count/2 4 for i in 0..<nums.count { 5 h -= nums[i] 6 } 7 return h 8 } 9 }
24ms
1 class Solution { 2 func missingNumber(_ nums: [Int]) -> Int { 3 var sum = 0 4 var max = 0 5 var i = 0 6 while i < nums.count { 7 max = max + i 8 sum = sum + nums[i] 9 i = i + 1 10 } 11 return max - sum + i 12 } 13 }
32ms:
求出从0~n的累加和,减去数组整体的和,那么由于数组内每个数字不相同,其差就是缺少的那个数字
1 class Solution { 2 func missingNumber(_ nums: [Int]) -> Int { 3 let count = nums.count 4 var sum = count + (count * (count - 1)) / 2 5 6 for i in 0..<count { 7 sum -= nums[i] 8 } 9 return sum 10 } 11 }
原文地址:https://www.cnblogs.com/strengthen/p/9756490.html
时间: 2024-09-30 07:03:42