codeforces #269 div2 D题（KMP）
2014-12-16 17:15:56
思路：考虑数与数间的关系，那么我们提取关系：数与前一个数的差，那么我们提取出n-1、w-1对关系，然后用w-1去匹配n-1即可，用kmp
1 #include <cstdio> 2 #include <cstring> 3 #include <cstdlib> 4 #include <cmath> 5 #include <vector> 6 #include <map> 7 #include <set> 8 #include <stack> 9 #include <queue> 10 #include <iostream> 11 #include <algorithm> 12 using namespace std; 13 #define lp (p << 1) 14 #define rp (p << 1|1) 15 #define getmid(l,r) (l + (r - l) / 2) 16 #define MP(a,b) make_pair(a,b) 17 typedef long long ll; 18 typedef unsigned long long ull; 19 const int INF = 1 << 30; 20 const int maxn = 200010; 21 22 int n,w; 23 int a[maxn],b[maxn],P[maxn]; 24 25 int main(){ 26 scanf("%d%d",&n,&w); 27 for(int i = 1; i <= n; ++i) scanf("%d",a + i); 28 for(int i = 1; i <= w; ++i) scanf("%d",b + i); 29 if(w == 1){ 30 printf("%d\n",n); 31 return 0; 32 } 33 for(int i = 1; i < n; ++i) a[i] = a[i + 1] - a[i]; 34 for(int i = 1; i < w; ++i) b[i] = b[i + 1] - b[i]; 35 int j = 0; 36 P[1] = 0; 37 for(int i = 2; i < w; ++i){ 38 while(j > 0 && b[j + 1] != b[i]) j = P[j]; 39 if(b[j + 1] == b[i]) j++; 40 P[i] = j; 41 } 42 j = 0; 43 int ans = 0; 44 for(int i = 1; i < n; ++i){ 45 while(j > 0 && b[j + 1] != a[i]) j = P[j]; 46 if(b[j + 1] == a[i]) j++; 47 if(j == w - 1) ++ans,j = P[j]; 48 } 49 printf("%d\n",ans); 50 return 0; 51 }
