hdu 1251 统计难题(字典树)

题目链接：hdu 1251 统计难题

题目大意：略。

解题思路：字典树水题，插入单个单词的时候，对路径上的节点+1，查询时返回最后落到节点的计数。

#include <cstdio>
#include <cstring>
#include <algorithm>

using namespace std;

const int maxn = 1000005;
const int sigma_size = 26;

struct Tire {
    int sz;
    int g[maxn][sigma_size];
    int val[maxn];

    void init();
    int idx(char ch);
    void insert(char* s);
    int find(char* s);
}S;

char op[maxn];

int main () {
    S.init();
    while (gets(op), strcmp(op, ""))
        S.insert(op);
    while (gets(op))
        printf("%d\n", S.find(op));
    return 0;
}

void Tire::init() {
    sz = 1;
    val[0] = 0;
    memset(g[0], 0, sizeof(g[0]));
}

int Tire::idx (char ch) {
    return ch - 'a';
}

int Tire::find(char* s) {
    int u = 0, n = strlen(s);

    for (int i = 0; i < n; i++) {
        int v = idx(s[i]);

        if (g[u][v] == 0)
            return 0;
        u = g[u][v];
    }
    return val[u];
}

void Tire::insert(char* s) {
    int u = 0, n = strlen(s);

    for (int i = 0; i < n; i++) {
        int v = idx(s[i]);

        if (g[u][v] == 0) {
            val[sz] = 0;
            memset(g[sz], 0, sizeof(g[sz]));
            g[u][v] = sz++;
        }

        u = g[u][v];
        val[u]++;
    }
}