Room and Moor
Time Limit: 12000/6000 MS (Java/Others) Memory Limit: 262144/262144 K (Java/Others)
Total Submission(s): 1288 Accepted Submission(s): 416
Problem Description
PM Room defines a sequence A = {A1, A2,..., AN}, each of which is either 0 or 1. In order to beat him, programmer Moor has to construct another sequence B = {B1, B2,... , BN} of the same length, which satisfies that:
Input
The input consists of multiple test cases. The number of test cases T(T<=100) occurs in the first line of input.
For each test case:
The first line contains a single integer N (1<=N<=100000), which denotes the length of A and B.
The second line consists of N integers, where the ith denotes Ai.
Output
Output the minimal f (A, B) when B is optimal and round it to 6 decimals.
Sample Input
4
9
1 1 1 1 1 0 0 1 1
9
1 1 0 0 1 1 1 1 1
4
0 0 1 1
4
0 1 1 1
Sample Output
1.428571
1.000000
0.000000
0.000000
Author
BUPT
Source
2014 Multi-University Training Contest 6
Recommend
We have carefully selected several similar problems for you: 5189 5184 5181 5180 5177
又一道G++ T,C++ AC 的好题!!!!
题意及题解转自:
http://blog.csdn.net/a601025382s/article/details/38423069
题意:
给定一个长度为n的,由0和1组成的序列ai,求一个序列bi,使得∑(bi-ai)^2最小。其中0<=bi<=1,bi<=b(i+1),bi为浮点型。输出最小的∑(bi-ai)^2的值。
题解:
对于ai序列中,开头的连续0,和结尾的连续1可以省略,因为bi中必定可以赋值连续0和连续1相同的值,使得(bi-ai)^2=0;
对于剩余的序列,我们可以分组,每组为连续1+连续0的形式(例如110010可以分成1100和10)。
对于每个组中的数ai,他们对应的bi必定是相同的。证:假设0对应的bi确定,那么要使∑(bi-ai)^2最小,1对应的bi肯定等于0对应bi中的最小值;同理1对应的bi确定时也一样。之后我们可以发现,这个值正好是rate=num1/(num1+num0),numi表示i的个数。
之后我们遍历每个分组,将每个组压入栈中。在压入栈之前,我们需要判断rate是否呈递增的,若是呈递增的,那么直接要入栈中,因为我们可以两个分组取不同的rate;若不是呈递增,那么我们需要将最后一个组出栈,然后合并,因为我们要保证bi的呈递增的;然后判断这个新的组入栈是否能是栈呈递增,不能则重复前面的动作,直到呈递增或者栈为空为止,之后将新的组压入栈中。
最后得到一个递增的栈,我们直到了每个分组的rate值,那么就能求∑(bi-ai)^2了。
13197281 | 2015-03-21 16:21:03 | Accepted | 4923 | 1638MS | 2408K | 2440 B | C++ | czy |
13197275 | 2015-03-21 16:20:38 | Time Limit Exceeded | 4923 | 6000MS | 2468K | 2440 B | G++ | czy |
1 #include <cstdio> 2 #include <cstring> 3 #include <stack> 4 #include <vector> 5 #include <algorithm> 6 7 #define ll long long 8 int const N = 100005; 9 int const M = 205; 10 int const inf = 1000000000; 11 ll const mod = 1000000007; 12 13 using namespace std; 14 15 int n; 16 double ans; 17 int aa[N]; 18 int a[N]; 19 int tot; 20 ll qcnt1[N]; 21 ll qcnt[N]; 22 int T; 23 24 void ini() 25 { 26 ans=0; 27 tot=0; 28 int i,j; 29 int st,en; 30 scanf("%d",&n); 31 for(i=1;i<=n;i++){ 32 scanf("%d",&aa[i]); 33 } 34 st=1; 35 while(st<=n){ 36 if(aa[st]==0){ 37 st++; 38 } 39 else{ 40 break; 41 } 42 } 43 if(st==n+1) return; 44 en=n; 45 while(en>st){ 46 if(aa[en]==1){ 47 en--; 48 } 49 else{ 50 break; 51 } 52 } 53 j=0; 54 for(i=st;i<=en;i++){ 55 j++; 56 a[j]=aa[i]; 57 } 58 tot=j; 59 //printf(" tot=%d\n",tot); 60 } 61 62 void solve() 63 { 64 int r; 65 r=0; 66 ll cnt1,cnt0; 67 ll cnt; 68 int i; 69 int now=1; 70 cnt1=cnt0=0; 71 for(i=1;i<=tot;i++){ 72 if(now==1){ 73 if(a[i]==1){ 74 cnt1++; 75 } 76 else{ 77 cnt0++; 78 now=0; 79 } 80 } 81 else{ 82 if(a[i]==0){ 83 cnt0++; 84 } 85 else{ 86 now=1; 87 cnt=cnt0+cnt1; 88 while(r!=0 && qcnt1[r]*cnt > qcnt[r]*cnt1 ){ 89 cnt1+=qcnt1[r]; 90 cnt+=qcnt[r]; 91 r--; 92 } 93 r++; 94 qcnt1[r]=cnt1; 95 qcnt[r]=cnt; 96 cnt0=0; 97 cnt1=1; 98 } 99 } 100 } 101 if(now==0){ 102 cnt=cnt0+cnt1; 103 while(r!=0 && qcnt1[r]*cnt > qcnt[r]*cnt1 ){ 104 cnt1+=qcnt1[r]; 105 cnt+=qcnt[r]; 106 r--; 107 } 108 r++; 109 qcnt1[r]=cnt1; 110 qcnt[r]=cnt; 111 } 112 double te; 113 //printf(" r=%d\n",r); 114 while(r!=0){ 115 te=1.0*qcnt1[r]/qcnt[r]; 116 ans+=(1-te)*(1-te)*qcnt1[r]+te*te*(qcnt[r]-qcnt1[r]); 117 r--; 118 } 119 } 120 121 void out() 122 { 123 printf("%.6f\n",ans); 124 } 125 126 int main() 127 { 128 //freopen("data.in","r",stdin); 129 scanf("%d",&T); 130 // for(cnt=1;cnt<=T;cnt++) 131 while(T--) 132 //while(scanf("%d",&n)!=EOF) 133 { 134 ini(); 135 solve(); 136 out(); 137 } 138 }