LeetCode Daily Question 15

3 月 22 日 每日一题

题目：287. Find the Duplicate Number

Given an array of integers nums containing n + 1 integers where each integer is in the range [1, n] inclusive.

There is only one repeated number in nums, return this repeated number.

You must solve the problem without modifying the array nums and uses only constant extra space.

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Example 1:

Input: nums = [1,3,4,2,2]
Output: 2
Example 2:

Input: nums = [3,1,3,4,2]
Output: 3

思路

hashmap 应该算这道题的暴力解法，等肝完 281project 之后可能会在这里更新其他方法。

代码

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class Solution {
public:
    int findDuplicate(vector<int>& nums) {
        unordered_map<int, int> counts;
        for(int i = 0; i < nums.size(); i ++){
            auto &iter = counts[nums[i]];
            iter++;
            if(iter == 2)
                return nums[i];
        }
        return -1;
    }
};