CodeForces

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

#include <cstdio>
#include <cstring>
using namespace std;

const int maxn = 2e5 + 10;
int ans, n, m;

void find_substring(int pattern[], int text[]) {
    vector<int> next(n + 1, 0);
    for (int i = 1; i < n; i++) {
        int j = i;
        while (j > 0) {
            j = next[j];
            if (pattern[j] == pattern[i]) {
                next[i + 1] = j + 1;
                break;
            }
        }
    }
    for (int i = 0, j = 0; i < m; i++) {
        if (j < n && text[i] == pattern[j]) {
            j++;
        } else {
            while (j > 0) {
                j = next[j];
                if (text[i] == pattern[j]) {
                    j++;
                    break;
                }
            }
        }
        if (j == n) ans++;
    }
}

int main(int argc, const char * argv[]) {
    int text[maxn], pattern[maxn];
    scanf("%d%d", &m, &n);
    for (int i = 0; i < m; i++) scanf("%d", &text[i]);
    for (int i = 0; i < n; i++) scanf("%d", &pattern[i]);
    for (int i = m - 1; i >= 1; i--) text[i] = text[i] - text[i - 1];
    for (int i = n - 1; i >= 1; i--) pattern[i] = pattern[i] - pattern[i - 1];
    --n; --m;
    find_substring(pattern + 1, text + 1);
    if (n == 0) ans++;
    printf("%d
", ans);
    return 0;
}