【HDU 1711】Number Sequence(裸KMP算法)

题目链接

题目链接 http://acm.hdu.edu.cn/showproblem.php?pid=1711

题意

裸KMP算法

时间复杂度

O(m+n)

代码如下(G++)

#include 
#include "string.h"
using namespace std;

int a[1000010];
int b[10010];
int next0[10010];

int T,N,M;
void get_next(){
    int i = 0;int j = -1;
    next0[0] = -1;
    while(i < M){
        if(j == -1||b[i] == b[j]){
            i++;j++; next0[i] = j;
        }else{
            j = next0[j];
        }
//        cout << i << " " << j << endl;
    }
}

int KMP(){
    int i = 0;int j = 0;
    while(i < N && j < M){
        if(j == -1 or a[i] == b[j])
            ++i,++j;
        else
            j = next0[j];
    }
    if(M == j) return i-j;
    else return -2;
}

int main() {
    ios::sync_with_stdio(false);
    cin >> T;

    while(T--){
        cin >> N >> M;
        for(int i = 0;i < N; ++i) cin >> a[i];
        for(int j = 0;j < M; ++j) cin >> b[j];
        get_next();
        cout << KMP()+1 << endl;
    }


    return 0;
}

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