HDU - 1711 Number Sequence （KMP模板）

题意：找最早匹配的位置

思路：KMP的模板题

#include <iostream>#include <cstdio>#include <cstring>#include <algorithm>using namespace std;const int MAXN = 1000010;int a[MAXN],b[MAXN],next[MAXN];int n,m;void getnext(int b[]){int i = 0,j = -1,len = m-1;next[0] = -1;while (i < len){if (j == -1 || b[i] == b[j]){i++,j++;next[i] = j;}else j = next[j];}}int kmp(int n,int m){int i = 0, j = 0;while (i < n && j < m){if (j == -1 || a[i] == b[j])i++,j++;else j = next[j];}if (j == m)return i-j+1;else return -1;}int main(){int t;scanf("%d",&t);while (t--){scanf("%d%d",&n,&m);for (int i = 0; i < n; i++)scanf("%d",&a[i]);for (int j = 0; j < m; j++)scanf("%d",&b[j]);getnext(b);printf("%d\n",kmp(n,m));}return 0;}