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“strcmp()” Anyone?
Input:Standard Input
Output:Standard Output
strcmp() is a library function in C/C++ which compares two strings. It takes two strings as input parameter and decides which one is lexicographically larger or smaller: If the first string is greater then it returns a positive value, if the second string is greater it returns a negative value and if two strings are equal it returns a zero. The code that is used to compare two strings in C/C++ library is shown below:
intstrcmp(char*s,char*t){inti;for(i=0; s[i]==t[i]; i++)if (s[i]==’\0′)return0;returns[i] – t[i];}
Figure: The standard strcmp() code provided for this problem.
The number of comparisons required to compare two strings in strcmp() function is never returned by the function. But for this problem you will have to do just that at a larger scale. strcmp() function continues to compare characters in the same position of the two strings until two different characters are found or both strings come to an end. Of course it assumes that last character of a string is a null (‘\0’) character. For example the table below shows what happens when “than” and “that”; “therE” and “the” are compared using strcmp() function. To understand how 7 comparisons are needed in both cases please consult the code block given above.
t
h
a
N
\0
t
h
e
r
E
\0
=
=
=
≠
=
=
=
≠
t
h
a
T
\0
t
h
e
\0
Returns negative value
7 Comparisons
Returns positive value
7 Comparisons
Input
The input file contains maximum 10 sets of inputs. The description of each set is given below:
Each set starts with an integer N (0<N<4001) which denotes the total number of strings. Each of the next N lines contains one string. Strings contain only alphanumerals (‘0’… ‘9’, ‘A’… ‘Z’, ‘a’… ‘z’) have a maximum length of 1000, and a minimum length of 1.
Input is terminated by a line containing a single zero. Input file size is around 23 MB.
Output
For each set of input produce one line of output. This line contains the serial of output followed by an integer T. This T denotes the total number of comparisons that are required in the strcmp() function if all the strings are compared with one another exactly once. So for N strings the function strcmp() will be called exactly
times. You have to calculate total number of comparisons inside the strcmp() function in those
calls. You can assume that the value of T will fit safely in a 64-bit signed integer. Please note that the most straightforward solution (Worst Case Complexity O(N2*1000)) will time out for this problem.
Sample InputOutput for Sample Input
2
a
b
4
cat
hat
mat
sir
0
Case 1: 1
Case 2: 6
Problem Setter: Shahriar Manzoor, Special Thanks:Md.Arifuzzaman Arif, Sohel Hafiz, Manzurur Rahman Khan
#include<iostream>#include<cstring>#include<algorithm>#include<cstdio>#include<string>#include<cstdlib>using namespace std;#define MAXN 4010*1000#define MAX 65int sz,t[MAXN][MAX];int jud[MAXN];int fin[MAXN];void clear(){sz=1;memset(t[0],-1,sizeof(t[0]));jud[0]=0;fin[0]=0;}int idx(char c){if(c<='9'&&c>='0')return c-'0';if(c<='Z'&&c>='A')return c-'A'+11;return c-'a'+37;}long long ret;void insert(char *s){int u=0;int n=strlen(s);ret+=jud[0];jud[0]++;for(int i=0;i<n;i++){int c=idx(s[i]);// cout<<t[u][c]<<" "<<u<<" "<<c<<endl;if(t[u][c]==-1){memset(t[sz],-1,sizeof(t[sz]));jud[sz]=0;fin[sz]=0;t[u][c]=sz++;}u=t[u][c];ret+=jud[u];ret+=jud[u];jud[u]++;}ret+=fin[u];fin[u]++;}int n;char str[2000];int main(){int cs=1;while(~scanf("%d",&n)&&n){ret=0;clear();for(int i=0;i<n;i++){scanf("%s",str);insert(str);}printf("Case %d: %lld\n",cs++,ret);}return 0;}
，同时也用对她的怀念来惩罚自己。
