hdu 1298 T9(字典树+DFS)

题目连接：hdu 1298 T9

题目大意：模拟手机打字的猜想功能，根据概率，每按一个按键，输出可能性最高的串。先给定N个单词，以及频率，

然后是Q次询问，每次询问给定一个按按键的顺序，以1为终止。

解题思路：对单词表建立字典树，每个节点有一个经过的频率，这个频率是根据所有经过该节点的单词频率总和。然后

DFS搜索一遍，将答案保存在ans中。

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

using namespace std;

const int maxn = 100005;
const int maxm = 105;
const int sigma_size = 26;
const char dir[15][10] = {"", "", "abc", "def", "ghi", "jkl", "mno", "pqrs", "tuv", "wxyz"};

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

    void init();
    int idx(char ch);
    void insert(char *s, int x);
}T;

int N, Q, c[maxm];
char ans[maxm][maxm], w[maxm], r[maxm];

void dfs (int d, int u) {
    if (d) {
        if (T.val[u] > c[d]) {
            c[d] = T.val[u];
            strncpy(ans[d], r, d);
        }
    }

    if (w[d] == 0 || w[d] == ‘1‘)
        return;

    int x = w[d] - ‘0‘;
    for (int i = 0; dir[x][i]; i++) {
        int v = dir[x][i] - ‘a‘;
        if (T.g[u][v] == 0)
            continue;
        r[d] = dir[x][i];
        dfs(d + 1, T.g[u][v]);
    }
}

int main () {
    int cas;
    scanf("%d", &cas);
    for (int kcas = 1; kcas <= cas; kcas++) {
        T.init();
        scanf("%d", &N);

        int x;
        for (int i = 0; i < N; i++) {
            scanf("%s%d", w, &x);
            T.insert(w, x);
        }

        printf("Scenario #%d:\n", kcas);
        scanf("%d", &Q);
        for (int i = 0; i < Q; i++) {
            scanf("%s", w);
            memset(c, 0, sizeof(c));

            dfs(0, 0);
            for (int x = 1; w[x-1] != ‘1‘; x++) {
    //            printf("<%c> %d:", w[x], c[x]);
                if (c[x] == 0)
                    printf("MANUALLY\n");
                else {
                    for (int j = 0; j < x; j++)
                        printf("%c", ans[x][j]);
                    printf("\n");
                }
            }
            printf("\n");
        }
        printf("\n");
    }
    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‘;
}

void Tire::insert(char* s, int x) {
    int u = 0, n = strlen(s);
    for (int i = 0; i < n; i++) {
        int v = idx(s[i]);

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