287. Find the Duplicate Number - Medium - Leetcode - 解題筆記 | Hsing Yu = = We are the dreamers. We make it happen 'cause we can see it.

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# 題目敘述

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.

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

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

利用 Set 資料結構來處理此題。

	public class Other {
	public int findDuplicate(int[] nums) {
	int slow = nums[0];
	int fast = nums[0];

	do{
	slow = nums[slow];
	fast = nums[nums[fast]];
	}while(slow != fast);

	slow = nums[0];

	while(slow != fast){
	slow = nums[slow];
	fast = nums[fast];
	}

	return slow;
	}
	}

	import java.util.HashSet;
	import java.util.Set;

	class Solution {
	public int findDuplicate(int[] nums) {
	Set<Integer> set = new HashSet<>();

	for(int num : nums){
	if(set.contains(num)){
	return num;
	}
	set.add(num);
	}

	return -1;
	}
	}

	#include <vector>
	using namespace std;

	class Solution {
	public:
	int findDuplicate(vector<int>& nums) {
	int slow = nums[0];
	int fast = nums[0];

	do{
	slow = nums[slow];
	fast = nums[nums[fast]];
	}while(slow != fast);

	slow = nums[0];

	while(slow != fast){
	slow = nums[slow];
	fast = nums[fast];
	}

	return slow;
	}
	};

單字

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