HDU 1711 - Number Sequence(kmp)

Problem link

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分析：

kmp匹配

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代碼：

_next[]數組的名字不能爲next[],否則會編譯出錯

#include <iostream>

using namespace std;

const int n = 1000010;
const int m = 10010;

int a[n], b[m];
int _next[m];

void get_next(int m)
{
    int i = 0, j;
    _next[0] = j = -1;
    while (i < m - 1) {
        if (j == -1 || b[j] == b[i]) {
            i++;
            j++;
            _next[i] = j;
        } else {
            j = _next[j];
        }
    }
}

int get_idx(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; 
        }
    }
    return -1; 
}

int main() 
{
    ios::sync_with_stdio(false);
    int t;
    cin >> t;
    while (t--) {
        int n, m;
        cin >> n >> m;
        for (int i = 0; i < n; ++i) {
            cin >> a[i];
        }
        for (int i = 0; i < m; ++i) {
            cin >> b[i];
        }
        get_next(m);
        int ans = get_idx(n, m);
        cout << ans << endl;
    }

    return 0;
}