CodeForces - 471D MUH and Cube Walls

Posted 2020-10-01 xFANx

 

CodeForces - 471D

 

记录差分，利用kmp对分别除去了第一个数的两个数组进行匹配

注意特判模式串长度为一的情况

 

 1 #include <cstdio>
 2 #include <cstring>
 3 using namespace std;
 4 
 5 const int maxn = 2e5 + 10;
 6 int ans, n, m;
 7 
 8 void find_substring(int pattern[], int text[]) {
 9     vector<int> next(n + 1, 0);
10     for (int i = 1; i < n; i++) {
11         int j = i;
12         while (j > 0) {
13             j = next[j];
14             if (pattern[j] == pattern[i]) {
15                 next[i + 1] = j + 1;
16                 break;
17             }
18         }
19     }
20     for (int i = 0, j = 0; i < m; i++) {
21         if (j < n && text[i] == pattern[j]) {
22             j++;
23         } else {
24             while (j > 0) {
25                 j = next[j];
26                 if (text[i] == pattern[j]) {
27                     j++;
28                     break;
29                 }
30             }
31         }
32         if (j == n) ans++;
33     }
34 }
35 
36 int main(int argc, const char * argv[]) {
37     int text[maxn], pattern[maxn];
38     scanf("%d%d", &m, &n);
39     for (int i = 0; i < m; i++) scanf("%d", &text[i]);
40     for (int i = 0; i < n; i++) scanf("%d", &pattern[i]);
41     for (int i = m - 1; i >= 1; i--) text[i] = text[i] - text[i - 1];
42     for (int i = n - 1; i >= 1; i--) pattern[i] = pattern[i] - pattern[i - 1];
43     --n; --m;
44     find_substring(pattern + 1, text + 1);
45     if (n == 0) ans++;
46     printf("%d\n", ans);
47     return 0;
48 }