Algorithm
Problem Name: 724. Find Pivot Index
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 = [1,7,3,6,5,6] Output: 3 Explanation: The pivot index is 3. Left sum = nums[0] + nums[1] + nums[2] = 1 + 7 + 3 = 11 Right sum = nums[4] + nums[5] = 5 + 6 = 11
Example 2:
Input: nums = [1,2,3] Output: -1 Explanation: There is no index that satisfies the conditions in the problem statement.
Example 3:
Input: nums = [2,1,-1] Output: 0 Explanation: The pivot index is 0. Left sum = 0 (no elements to the left of index 0) Right sum = nums[1] + nums[2] = 1 + -1 = 0
Constraints:
1 <= nums.length <= 104-1000 <= nums[i] <= 1000
Code Examples
#1 Code Example with C++ Programming
Code -
C++ Programming
class Solution {
public:
int pivotIndex(vector<int>& nums) {
int n = nums.size(), left = 0, right = 0;
for(int x: nums) right += x;
for(int i = 0; i < n; left += nums[i], right -= nums[i], i++)
if(left == right - nums[i]) return i;
return -1;
}
};
Input
Output
#2 Code Example with Java Programming
Code -
Java Programming
class Solution {
public int pivotIndex(int[] nums) {
int n = nums.length;
int sum = 0;
for (int i = 0; i < n; i++) {
sum += nums[i];
}
int leftSum = 0;
for (int i = 0; i < n; i++) {
if (leftSum == sum - leftSum - nums[i]) {
return i;
}
leftSum += nums[i];
}
return -1;
}
}
Input
Output
#3 Code Example with Javascript Programming
Code -
Javascript Programming
start coding...<
const pivotIndex = function(nums) {
let sum = 0;
let leftSum = 0;
nums.forEach(num => {sum += num});
for (let i = 0; i < nums.length; i++) {
if (leftSum === sum - leftSum - nums[i]) return i;
leftSum += nums[i];
}
return -1;
};
Input
Output
#4 Code Example with Python Programming
Code -
Python Programming
class Solution:
def pivotIndex(self, nums: List[int]) -> int:
sm = sum(nums)
cur = 0
for i in range(len(nums)):
if cur == sm - cur - nums[i]:
return i
cur += nums[i]
return -1
Input
Output
#5 Code Example with C# Programming
Code -
C# Programming
namespace LeetCode
{
public class _0724_FindPivotIndex
{
public int PivotIndex(int[] nums)
{
var sum = 0;
foreach (var num in nums)
sum += num;
var leftSum = 0;
for (int i = 0; i < nums.Length; i++)
{
if (leftSum == sum - leftSum - nums[i]) return i;
leftSum += nums[i];
}
return -1;
}
}
}
Input