【朱迪的LeetCode刷题笔记】724. Find Pivot Index #Easy #Python
本帖最后由 Judie 于 2023-5-23 02:22 编辑Given an array of integers nums, calculate the pivot index of this array.
The pivot index is the index where the sum of all the numbers strictly to the left of the index is equal to the sum of all the numbers strictly to the index's right.
If the index is on the left edge of the array, then the left sum is 0 because there are no elements to the left. This also applies to the right edge of the array.
Return the leftmost pivot index. If no such index exists, return -1.
Example 1:
Input: nums =
Output: 3
Explanation:
The pivot index is 3.
Left sum = nums + nums + nums = 1 + 7 + 3 = 11
Right sum = nums + nums = 5 + 6 = 11
Example 2:
Input: nums =
Output: -1
Explanation:
There is no index that satisfies the conditions in the problem statement.
Example 3:
Input: nums =
Output: 0
Explanation:
The pivot index is 0.
Left sum = 0 (no elements to the left of index 0)
Right sum = nums + nums = 1 + -1 = 0
Constraints:
1 <= nums.length <= 104
-1000 <= nums <= 1000
Note: This question is the same as 1991: https://leetcode.com/problems/find-the-middle-index-in-array/
class Solution(object):
def pivotIndex(self, nums):
"""
:type nums: List
:rtype: int
"""
Hint
(1/3)
**** Hidden Message *****
Hint
(2/3)
**** Hidden Message *****
Hint
(3/3)
**** Hidden Message *****
Judy
python version cs way?
class Solution(object):
def pivotIndex(self, nums):
"""
:type nums: List
:rtype: int
"""
tempLeft = 0
tempRight = sum(nums)
for i, n in enumerate(nums):
tempRight -= n
if tempLeft == tempRight:
return i
tempLeft += n
return -1
Gray
c++ version math way?
class Solution {
public:
int pivotIndex(vector<int>& nums) {
int total=0;
for(int i = 0; i < nums.size(); i++){
total += nums;
}
int temp = 0;
if(total-nums==0){
return 0;
}
for(int i = 0; i < nums.size()-1;i++){
temp = nums + temp;
if((total-nums) == temp*2){
return i+1;
}
}
return -1;
}
};
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