455:Periodic Strings
A character string is said to have period k if it can be formed by concatenating one or more repetitionsof another string of length k. For example, the string ”abcabcabcabc” has period 3, since it is formedby 4 repetitions of the string ”abc”. It also has periods 6 (two repetitions of ”abcabc”) and 12 (onerepetition of ”abcabcabcabc”).
Write a program to read a character string and determine its smallest period.
Input
The first line oif the input file will contain a single integer N indicating how many test case that yourprogram will test followed by a blank line. Each test case will contain a single character string of upto 80 non-blank characters. Two consecutive input will separated by a blank line.
Output
An integer denoting the smallest period of the input string for each input. Two consecutive output areseparated by a blank line.
Sample Input
1
HoHoHo
Sample Output
2
开始的代码如下没过,原因是我判断 i 是否是字符串周期的时候并没有事先判断字符串长度是否能被 i 整除:
#include<cstdio>
#include<cstring>
#define maxn 80 + 5
char s[maxn];
int main(){
int T;
scanf("%d",&T);
while(T--){
scanf("%s",s);
int n = strlen(s),i;
for(i = 1;i <= n/2;i++){
int mark = 1;
for(int k = 0;k < i;k++){
for(int j = i + k;j < n;j += i){
if(s[j] != s[j-i]) mark = 0;
}
}
if(mark){
printf("%d\n",i);
break;
}
}
if(i > n/2) printf("%d\n",n);
}
return 0;
}
修改之后的代码:
#include<cstdio>
#include<cstring>
#define maxn 80 + 5
char s[maxn];
int main(){
int T;
scanf("%d",&T);
while(T--){
scanf("%s",s);
int n = strlen(s),i;
for(i = 1;i <= n/2;i++){
if(!(n%i)){
int mark = 1;
for(int k = 0;k < i;k++){
for(int j = i + k;j < n;j += i){
if(s[j] != s[j-i]) mark = 0;
}
}
if(mark){
printf("%d\n",i);
break;
}
}
}
if(i > n/2) printf("%d\n",n);
if(T) putchar('\n');
}
return 0;
}
参考别人的代码:
#include<cstdio>
#include<cstring>
#define maxn 80 + 5
char s[maxn];
int main(){
int T;
scanf("%d",&T);
while(T--){
scanf("%s",s);
int len = strlen(s),i,k;
for(i = 1;i <= len;i++){
if(!(len % i)){
//判断是否是周期串直接对 i 求余即可,比我之前的好多了
for(k = 0;k < len;k++){
if(s[k] != s[k % i]) break;
}
if(k == len){
printf("%d\n",i);
break;
}
}
}
if(T) putchar('\n');
}
return 0;
}