lightoj1224 DNA Prefix

题意：给定n个字符串，求拥有前缀a[0…l]的字符串个数x乘上这个字符串长度，求这个最大值。

思路：建立棵字典树，每个节点纪录上经过这个节点的字符串个数，然后dfs求解。

struct node {
    int cnt;
    node* nxt[4];
    node() {
        for (int i = 0;i < 4;++i)
            nxt[i] = NULL;
        cnt = 0;
    }
}*root;
char s[60];
int id(char c) {
    if (c == 'A') return 0;
    if (c == 'C') return 1;
    if (c == 'G') return 2;
    return 3;
}
void insert(char* str) {
    int len = strlen(str);
    node* p = root;
    for (int i = 0;i < len;++i) {
        int idx = id(str[i]);
        if (p->nxt[idx] == NULL) p->nxt[idx] = new node();
        p = p->nxt[idx];
        p->cnt++;
    }
}
void del(node* p) {
    if (p == NULL) return ;
    for (int i = 0;i < 4;++i)
        del(p->nxt[i]);
    delete p;
}
int maxNum;
void dfs(node* p, int depth) {
    for (int i = 0;i < 4;++i) {
        if (p->nxt[i] != NULL) {
            dfs(p->nxt[i], depth + 1);
        }
    }
    if (p->cnt * depth > maxNum) {
        maxNum = p->cnt * depth;
    }
}
int main(int argc, const char * argv[])
{   
    // freopen("in.txt","r",stdin);
    // freopen("out.txt","w",stdout);
    int n, t;
    cin >> t;
    while(t--) {
        cin >> n;
        root = new node();
        for (int i = 0;i < n;++i) {
            scanf("%s", s);
            insert(s);
        }
        maxNum = 0;
        dfs(root, 0);
        printf("Case %d: %d\n", ++nCase, maxNum);
        del(root);
    }
    return 0;
}