<LeetCode OJ>Missing Number【268】

268. Missing Number

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Question

Total Accepted: 31740 Total
Submissions: 83547 Difficulty: Medium

Given an array containing n distinct numbers taken from 0,
1, 2, ..., n, find the one that is missing from the array.

For example,

Given nums = [0, 1, 3] return 2.

Note:

Your algorithm should run in linear runtime complexity. Could you implement it using only constant extra space complexity?

Credits:

Special thanks to @jianchao.li.fighter for adding this problem and creating all test cases.

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Array Math Bit
Manipulation

Hide Similar Problems

(H) First Missing Positive (M)
Single Number (H) Find the Duplicate Number

//思路首先：
//我真服了这个题，题意理解错了，我还以为是干嘛呢！
//后来才明白原来是随机从0到size()选取了一些数，其中有一个丢失了，草
//别人的算法：数学推出，0到size()的总和减去当前数组和sum

class Solution {
public:
    int missingNumber(vector<int>& nums) {
        int sum = 0;
        for(int num: nums)
            sum += num;
        int n = nums.size();
        return (n * (n + 1))/ 2 - sum;
    }
};