Topic describes

Find duplicate numbers in the array.

All numbers in an array of length N, nums, are in the range 0 to n-1. Some numbers in the array are repeated, but we don’t know how many are repeated, or how many times each number is repeated. Please find any duplicate number in the array.

The subject sample

Input:2.3.1.0.2.5.3] output:2 或 3 
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Subject analysis

To find duplicate numbers in an array, use the Map method, using key-value pairs

Code implementation

/ * * *@param {number[]} nums
 * @return {number}* /
var findRepeatNumber = function(nums) {
    const map = new Map(a);for (let i = 0; i < nums.length; i++) {
        if (map.has(nums[i])) return nums[i]
        map.set(nums[i], 1)}return null;
};
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Title source

LeetCode refers to the duplicate number in Offer 03