Acperience
Time Limit: 4000/2000 MS (Java/Others) Memory Limit: 65536/65536 K (Java/Others)
Total Submission(s): 220 Accepted Submission(s): 119
Problem Description
Deep
neural networks (DNN) have shown significant improvements in several
application domains including computer vision and speech recognition. In
computer vision, a particular type of DNN, known as Convolutional
Neural Networks (CNN), have demonstrated state-of-the-art results in
object recognition and detection.
Convolutional neural networks
show reliable results on object recognition and detection that are
useful in real world applications. Concurrent to the recent progress in
recognition, interesting advancements have been happening in virtual
reality (VR by Oculus), augmented reality (AR by HoloLens), and smart
wearable devices. Putting these two pieces together, we argue that it is
the right time to equip smart portable devices with the power of
state-of-the-art recognition systems. However, CNN-based recognition
systems need large amounts of memory and computational power. While they
perform well on expensive, GPU-based machines, they are often
unsuitable for smaller devices like cell phones and embedded
electronics.
In order to simplify the networks, Professor Zhang
tries to introduce simple, efficient, and accurate approximations to
CNNs by binarizing the weights. Professor Zhang needs your help.
More specifically, you are given a weighted vector W = (w1,w2,...,wn). Professor Zhang would like to find a binary vector B = (b1,b2,...,bn)(bi∈{+1,-1}) and a scaling factor α≥0 in such a manner that ||W-αB|| 2 is minimum.
Note that ||.|| denotes the Euclidean norm (i.e.||X|| = √ x12+...+xn2, where X = (x1,x2,...,xn).
Input
There are multiple test cases. The first line of input contains an integer T, indicating the number of test cases. For each test case:
The first line contains an integers n (1≤n≤100000) -- the length of the vector. The next line contains n integers: w1,w2,...,wn (−10000≤wi≤10000).
Output
For each test case, output the minimum value of ||W-αB|| 2 as an irreducible fraction "p/q" where re integers, q>0.
Sample Input
3
4
1 2 3 4
4
2 2 2 2
5
5 6 2 3 4
Sample Output
Author
zimpha
Source
解析：
i=1?n??w?i?2??−?n??1??(?i=1?∑?n??∣w?i??∣)?2??
1 #include <bits/stdc++.h>
2
3 typedef long long ll;
4
5 ll gcd(ll a, ll b)
6 {
7 return b == 0 ? a : gcd(b, a%b);
8 }
9
10 int main()
11 {
12 int T, n;
13 scanf("%d", &T);
14 while(T--){
15 scanf("%d", &n);
16 ll w1 = 0, w2 = 0;
17 for(int i = 0, wi; i < n; ++i){
18 scanf("%d", &wi);
19 w1 += wi*wi;
20 w2 += abs(wi);
21 }
22 ll a = w1*n-w2*w2, b = n;
23 ll g = gcd(a, b);
24 printf("%I64d/%I64d\n", a/g, b/g);
25 }
26 return 0;
27 }
HDU 5734 Acperience
原文：http://www.cnblogs.com/inmoonlight/p/5693169.html
