【UVA】11732 - strcmp() Anyone?

一开始不知道这种一维建树方法。

每次一层用一个链指向下一层最左边的结点，之后每一层用一个链表串联所有的结点，这样就建树成功了。

14328524

11732

strcmp() Anyone?

Accepted

C++

0.826

2014-10-09 13:13:14

#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;
typedef long long LL;
typedef pair<int,int> pill;
const int nodemaxn = 4000 * 1000 + 100;
struct Trie{
    int head[nodemaxn]; //左儿子链
    int next[nodemaxn]; //右兄弟链
    int   ch[nodemaxn]; //这个结点代表的字符
    LL   tot[nodemaxn]; //有几个单词经过了这个结点
    int   sz;           //结点个数
    LL   ret;           //比较的次数
    void clear(){
        head[0] = 0; next[0] = 0; tot[0] = 0; sz = 1; ret = 0;
    }
    void insert(char *str){
        int L = strlen(str);
        int u = 0,v,found;
        tot[0]++;
        for(int i = 0; i <= L; i ++){
            found = 0;
            for(v = head[u]; v != 0 ; v = next[v]){  //到下一层去找
                if(ch[v] == str[i]){
                    found = 1;
                    break;
                }
            }
            if(!found){  //如果没有找到
                v = sz ++;
                tot[v] = 0;
                ch[v] = str[i];
                next[v] = head[u];
                head[u] = v;
                head[v] = 0;
            }
            u = v;
            tot[u] ++;
        }
    }
    void dfs(int u,int depth){
        if(head[u] == 0){
            ret += tot[u] * (tot[u] - 1) * depth;
        }
        else{
            LL sum = 0;
            for(int v = head[u] ; v != 0; v = next[v])
                sum += tot[v] * (tot[u] - tot[v]);
            ret += sum / 2 * (2 * depth + 1);
            for(int v = head[u] ; v != 0; v = next[v])
                dfs(v,depth + 1);
        }
    }
}trie;
const int maxn = 4000 + 10;
int main(){
    int n,Case = 1;
    while(scanf("%d",&n) && n){
        trie.clear();
        for(int i = 0; i < n; i++){
            char str[maxn];
            scanf("%s",str);
            trie.insert(str);
        }
        trie.dfs(0,0);
        printf("Case %d: %lld\n",Case++,trie.ret);
    }
}