原题链接：HDU4162
题目大意：稍加伪装的最小表示法模板题。
最小表示法
读入字符串后，比较 $str[i]$ 逆时针走多少步可以变成 $str[i+1]$。然后这些步数构成的字符串，求它的最小表示。
- 下标从 $1$ 开始（模板来自《算法竞赛进阶指南》）
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#include <iostream>
#include <algorithm>
#include <cstring>
#include <cstdio>
using namespace std;
const int N = 300010;
char str[N];
char res[N * 2];
int calc(int a, int b) {
int t = 0;
while (a != b) a = (a + 1) % 8, t++;
return t;
}
int get_min(char s[]) {
int n = strlen(s + 1);
for (int i = 1; i <= n; i++) s[n + i] = s[i];
int i = 1, j = 2, k;
while (i <= n && j <= n) {
for (k = 0; k < n && s[i + k] == s[j + k]; k++);
if (k == n) break;
s[i + k] > s[j + k] ? i = i + k + 1 : j = j + k + 1;
if (i == j) i++;
}
return min(i, j);
}
int main() {
while (scanf("%s", str) != EOF) {
memset(res, 0, sizeof res);
int n = strlen(str);
str[n] = str[0], str[n + 1] = '\0';
for (int i = 0, k = 0; i < n; i++) {
res[++k] = calc(str[i] - '0', str[i + 1] - '0') + 48;
}
int st = get_min(res);
res[st + n] = '\0';
puts(res + st);
}
return 0;
}
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- 下标从 $0$ 开始（模板来自 OI-Wiki ）
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#include <iostream>
#include <algorithm>
#include <cstring>
#include <cstdio>
using namespace std;
const int N = 300010;
char str[N];
char res[N * 2];
int calc(int a, int b) {
int t = 0;
while (a != b) a = (a + 1) % 8, t++;
return t;
}
int get_min(char s[]) {
int n = strlen(s);
int k = 0, i = 0, j = 1;
while (k < n && i < n && j < n) {
if (s[(i + k) % n] == s[(j + k) % n]) {
k++;
} else {
s[(i + k) % n] > s[(j + k) % n] ? i = i + k + 1 : j = j + k + 1;
if (i == j) i++;
k = 0;
}
}
return min(i, j);
}
int main() {
while (scanf("%s", str) != EOF) {
memset(res, 0, sizeof res);
int n = strlen(str);
str[n] = str[0], str[n + 1] = '\0';
for (int i = 0; i < n; i++) {
res[i] = calc(str[i] - '0', str[i + 1] - '0') + 48;
}
int st = get_min(res);
for (int i = st; i < n; i++) putchar(res[i]);
for (int i = 0; i < st; i++) putchar(res[i]);
puts("");
}
return 0;
}
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