字符串训练之四

https://www.luogu.org/problem/P2264

看一眼就是水题

方法应该很多，都可以乱搞出来

我就找了两个比较好的做法

一个是trie，还有一个是set

trie

#include<cstdio>
#include<cstring>
#include<cstdlib>
#include<cmath>
#include<queue>
#include<stack>
#include<map>
#include<set>
#include<iostream>
#include<algorithm>
#include<string>
#define rep(i,x,y) for(register int i = x;i <= y;++i)
#define repd(i,x,y) for(register int i = x;i >= y;--i)
using namespace std;
typedef long long ll;
int n,sz,ans,cnt = 1,val[1000000];
char trie[100000][27];
void trie_build(char*s,int len)
{
    int x = 0;
    rep(i,1,len) {
        if(!trie[x][s[i]]) trie[x][s[i]] = ++sz;
        x = trie[x][s[i]];
    }
    val[x] = -1;
}

bool trie_find(char*s,int len)
{
    int x = 0;
    rep(i,1,len)
    {
        if(s[i] < 'a' || s[i] > 'z' || !trie[x][s[i]]) return false;
        x = trie[x][s[i]];
    }
    if(val[x] != cnt && val[x])return val[x] = cnt,true;
    return false;
}

int main()
{
    freopen("qs.in","r",stdin);
    scanf("%d",&n);getchar();
    char s[100],c;
    int len;
    rep(i,1,n) {
        len = 0;
        while((c = getchar()) != '\n' && c != ' ') {
            if(c >= 'A' && c <= 'Z') c += 32;
            s[++len] = c;
        }
        trie_build(s,len);
    }
    len = 0;
    while((c = getchar()) != EOF)
    {
        if(c == ' ' || c == '.' || c == ',') {
            if(trie_find(s,len)) ans++;
            len = 0; if(c == '.') ++cnt;
            continue;
        }
        if(c >= 'A' && c <= 'Z') c += 32;
        s[++len] = c;
    }
    if(trie_find(s,len)) ans++;
    cout<<ans;
    return 0;
}

set

#include<bits/stdc++.h>
using namespace std;
set<string>se,se2;
int ans,n;
int main()
{
    scanf("%d",&n);
    string a;
    for(int i=1;i<=n;i++){
        cin>>a;
        for(int i=0;i<a.length();i++)
            if(a[i]>='a'&&a[i]<='z') a[i]-=32;
        se.insert(a);
    }
    char ch=getchar();
    string b;
    while(scanf("%c",&ch)==1){
        if(ch=='\n')break;
        if((ch>='A'&&ch<='Z')||(ch>='a'&&ch<='z')){
            if(ch>='a'&&ch<='z')ch=ch-32;
            b+=ch;
        }
        else{
            if(!b.empty()){
                if(se.count(b))se2.insert(b);
                b.clear();
            }
            if(ch=='.')ans+=se2.size(),se2.clear();
        }
    }
    printf("%d\n",ans);
    return 0;
}

原文地址：https://www.cnblogs.com/wzxbeliever/p/11624872.html