Array
Dynamic Programming
Description
An integer array is called arithmetic if it consists of at least three elements and if the difference between any two consecutive elements is the same.
For example, [1,3,5,7,9]
, [7,7,7,7]
, and [3,-1,-5,-9]
are arithmetic sequences.
Given an integer array nums
, return the number of arithmetic subarrays of nums
.
A subarray is a contiguous subsequence of the array.
Example 1:
Input: nums = [1,2,3,4]
Output: 3
Explanation: We have 3 arithmetic slices in nums: [1, 2, 3], [2, 3, 4] and [1,2,3,4] itself.
Example 2:
Input: nums = [1]
Output: 0
Constraints:
1 <= nums.length <= 5000
-1000 <= nums[i] <= 1000
Solutions
Solution 1
Python3 Java C++ Go TypeScript
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12 class Solution :
def numberOfArithmeticSlices ( self , nums : List [ int ]) -> int :
ans , cnt = 0 , 2
d = 3000
for a , b in pairwise ( nums ):
if b - a == d :
cnt += 1
else :
d = b - a
cnt = 2
ans += max ( 0 , cnt - 2 )
return ans
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16 class Solution {
public int numberOfArithmeticSlices ( int [] nums ) {
int ans = 0 , cnt = 0 ;
int d = 3000 ;
for ( int i = 0 ; i < nums . length - 1 ; ++ i ) {
if ( nums [ i + 1 ] - nums [ i ] == d ) {
++ cnt ;
} else {
d = nums [ i + 1 ] - nums [ i ] ;
cnt = 0 ;
}
ans += cnt ;
}
return ans ;
}
}
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17 class Solution {
public :
int numberOfArithmeticSlices ( vector < int >& nums ) {
int ans = 0 , cnt = 0 ;
int d = 3000 ;
for ( int i = 0 ; i < nums . size () - 1 ; ++ i ) {
if ( nums [ i + 1 ] - nums [ i ] == d ) {
++ cnt ;
} else {
d = nums [ i + 1 ] - nums [ i ];
cnt = 0 ;
}
ans += cnt ;
}
return ans ;
}
};
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14 func numberOfArithmeticSlices ( nums [] int ) ( ans int ) {
cnt , d := 0 , 3000
for i , b := range nums [ 1 :] {
a := nums [ i ]
if b - a == d {
cnt ++
} else {
d = b - a
cnt = 0
}
ans += cnt
}
return
}
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17 function numberOfArithmeticSlices ( nums : number []) : number {
let ans = 0 ;
let cnt = 0 ;
let d = 3000 ;
for ( let i = 0 ; i < nums . length - 1 ; ++ i ) {
const a = nums [ i ];
const b = nums [ i + 1 ];
if ( b - a == d ) {
++ cnt ;
} else {
d = b - a ;
cnt = 0 ;
}
ans += cnt ;
}
return ans ;
}
Solution 2
GitHub