## 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;
}
};
``````
Copy The Code &

Input

cmd
nums = [1,7,3,6,5,6]

Output

cmd
3

### #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;
}
}
``````
Copy The Code &

Input

cmd
nums = [1,7,3,6,5,6]

Output

cmd
3

### #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;
};
``````
Copy The Code &

Input

cmd
nums = [1,2,3]

Output

cmd
-1

### #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
``````
Copy The Code &

Input

cmd
nums = [1,2,3]

Output

cmd
-1

### #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;
}
}
}
``````
Copy The Code &

Input

cmd
nums = [2,1,-1]