c++学习笔记——前缀和

题目描述：

代码实现：

#include<iostream>
using namespace std;
int arr1[1010];
int arr2[1010] = { 0 };
int arr3[1010] = { 0 };

int main() 
{
	int n;
	int maxa = 0;
	int mina = 1000;

	cin >> n;
	for (int i = 0; i < n; i++)
	{
		cin >> arr1[i];
		maxa = max(maxa, arr1[i]);
		mina = min(mina, arr1[i]);

		arr2[arr1[i]]++;
		arr3[arr1[i]]++;

	}
	for (int i = 1; i < maxa + 1; i++)
	{
		arr2[i] += arr2[i - 1];
	}
	for (int i = maxa - 1; i >= mina - 1; i--)
	{
		arr3[i] += arr3[i + 1];
	}
	for (int i = 0; i < n; i++)
	{
		if (arr2[arr1[i]] == arr3[arr1[i]])
		{
			cout << arr1[i];
			return 0;
		}
	}
	cout << "-1";
	return 0;
}