Codeforces Round #245 (Div. 一)D(最近点对)

Codeforces Round #245 (Div. 1)D(最近点对)
D. Tricky Function
time limit per test
2 seconds
memory limit per test
256 megabytes
input
standard input
output
standard output

Iahub and Sorin are the best competitive programmers in their town. However, they can't both qualify to an important contest. The selection will be made with the help of a single problem. Blatnatalag, a friend of Iahub, managed to get hold of the problem before the contest. Because he wants to make sure Iahub will be the one qualified, he tells Iahub the following task.

You're given an (1-based) array a with n elements. Let's define function f(i, j) (1 ≤ i, j ≤ n) as (i - j)2 + g(i, j)2. Function g is calculated by the following pseudo-code:

int g(int i, int j) {
    int sum = 0;
    for (int k = min(i, j) + 1; k <= max(i, j); k = k + 1)
        sum = sum + a[k];
    return sum;
}

Find a value mini ≠ j  f(i, j).

Probably by now Iahub already figured out the solution to this problem. Can you?

Input

The first line of input contains a single integer n (2 ≤ n ≤ 100000). Next line contains n integers a[1]a[2], ..., a[n]( - 104 ≤ a[i] ≤ 104).

Output

Output a single integer — the value of mini ≠ j  f(i, j).

Sample test(s)
input
4
1 0 0 -1
output
1
input
2
1 -1
output
2
不难看出 f(i,j)=(j-i)^2+(sum[j]-sum[i])^2 , 于是可以将(i,sum[i])看成平面上的点,则问题转化为了在一个2D平面上求最近点对的距离,用分治法实现:

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