AC了,求关注

#include <iostream>
using namespace std;
const int N = 1e5+5;
int prevnum[N];
int main()
{
	int n, num;
	int maxLength = 0;
	cin >> n;
	for ( int i = 1; i <= n; ++i ) {
		cin >> num;
		prevnum[i] = prevnum[i-1] + num;
	}
	
	for ( int i = 1; i <= n; ++i ) {
		int j;
		if ( !maxLength ) j = i+1;//maxLength没有被更新过，就从区间长度2开始
		else j = i + maxLength - 1;
		
		for ( ; j <= n; j += 2 ) {
            //区间长度的一半 == 区间和
			if ( (j-i+1)/2 == prevnum[j]-prevnum[i-1] ) {
				maxLength = max(maxLength, j-i+1);
			}
		}
	}
	
	cout << maxLength << '\n';
	return 0;
}