1207. Unique Number of Occurrences

题目

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.

Example 1:

Input: arr = [1,2,2,1,1,3]
Output: true
Explanation: The value 1 has 3 occurrences, 2 has 2 and 3 has 1. No two values have the same number of occurrences.

Example 2:

Input: arr = [1,2]
Output: false

Example 3:

Input: arr = [-3,0,1,-3,1,1,1,-3,10,0]
Output: true

Constraints:

1 <= arr.length <= 1000
-1000 <= arr[i] <= 1000

题目大意

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。

提示：

1 <= arr.length <= 1000
-1000 <= arr[i] <= 1000

解题思路

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。
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。

代码


package leetcode

func uniqueOccurrences(arr []int) bool {
	freq, m := map[int]int{}, map[int]bool{}
	for _, v := range arr {
		freq[v]++
	}
	for _, v := range freq {
		if _, ok := m[v]; !ok {
			m[v] = true
		} else {
			return false
		}
	}
	return true
}