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45 lines
1.1 KiB
Markdown
Executable File
45 lines
1.1 KiB
Markdown
Executable File
# [1207. Unique Number of Occurrences](https://leetcode.com/problems/unique-number-of-occurrences/)
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## 题目
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Given an array of integers `arr`, write a function that returns `true` if and only if the number of occurrences of each value in the array is unique.
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**Example 1:**
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Input: arr = [1,2,2,1,1,3]
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Output: true
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Explanation: The value 1 has 3 occurrences, 2 has 2 and 3 has 1. No two values have the same number of occurrences.
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**Example 2:**
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Input: arr = [1,2]
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Output: false
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**Example 3:**
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Input: arr = [-3,0,1,-3,1,1,1,-3,10,0]
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Output: true
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**Constraints:**
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- `1 <= arr.length <= 1000`
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- `-1000 <= arr[i] <= 1000`
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## 题目大意
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给你一个整数数组 arr，请你帮忙统计数组中每个数的出现次数。如果每个数的出现次数都是独一无二的，就返回 true；否则返回 false。
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提示：
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- 1 <= arr.length <= 1000
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- -1000 <= arr[i] <= 1000
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## 解题思路
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- 给出一个数组，先统计每个数字出现的频次，判断在这个数组中是否存在相同的频次。
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- 简单题，先统计数组中每个数字的频次，然后用一个 map 判断频次是否重复。
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