描述
Given an array of integers arr, and three integers a, b and c. You need to find the number of good triplets.
A triplet (arr[i], arr[j], arr[k]) is good if the following conditions are true:
- 0 <= i < j < k < arr.length
- |arr[i] - arr[j]| <= a
- |arr[j] - arr[k]| <= b
- |arr[i] - arr[k]| <= c
Where |x| denotes the absolute value of x.
Return the number of good triplets.
Example 1:
Input: arr = [3,0,1,1,9,7], a = 7, b = 2, c = 3
Output: 4
Explanation: There are 4 good triplets: [(3,0,1), (3,0,1), (3,1,1), (0,1,1)].
Example 2:
Input: arr = [1,1,2,2,3], a = 0, b = 0, c = 1
Output: 0
Explanation: No triplet satisfies all conditions.
Note:
3 <= arr.length <= 100
0 <= arr[i] <= 1000
0 <= a, b, c <= 1000
解析
根据题意，只需要在进行三重 for 循环的时候，判断是否满足给出的三个限制条件即可，这里有一个小的技巧，就是在二重 for 循环的时候先判断 abs(arr[i] - arr[j]) <= a 是否成立，这样可以缩短提交的时间。
解答
class Solution(object):
def countGoodTriplets(self, arr, a, b, c):
"""
:type arr: List[int]
:type a: int
:type b: int
:type c: int
:rtype: int
"""
n = len(arr)
r = 0
for i in range(n-2):
for j in range(i+1,n-1):
if abs(arr[i] - arr[j]) <= a:
for k in range(j+1,n):
if abs(arr[j]-arr[k])<=b and abs(arr[i]-arr[k])<=c:
r += 1
return r
运行结果
Runtime: 324 ms, faster than 86.44% of Python online submissions for Count Good Triplets.
Memory Usage: 13.5 MB, less than 64.45% of Python online submissions for Count Good Triplets.
原题链接：https://leetcode.com/problems/count-good-triplets/