UVALive 6507 Passwords

Passwords

Time Limit: 3000ms

Memory Limit: 131072KB

This problem will be judged on UVALive. Original ID: 6507
64-bit integer IO format: %lld      Java class name: Main

 

解题：好高深的hash啊

#include <bits/stdc++.h>
using namespace std;
typedef long long LL;
const int maxn = 205;
const int base = 233;
const int mod = 1e9+7;
char str[maxn][20010];
LL hs[maxn][20010],B[20010];
int n;
unordered_map<LL,int>ump;
void init(){
    B[0] = 1;
    for(int i = 1; i < 20010; ++i)
        B[i] = B[i-1]*base%mod;
}
LL calc(int i,int L,int R){
    return ((hs[i][R] - hs[i][L-1]*B[R - L + 1])%mod + mod)%mod;
}
void solve(){
    ump.clear();
    for(int i = 0; i < n; ++i){
        for(int j = 1,len = strlen(str[i] + 1); j <= len; ++j){
            hs[i][j] = (hs[i][j-1]*base + str[i][j])%mod;
            ump[hs[i][j]]++;
        }
    }
    int a = 0,b = 0;
    for(int i = 0; i < n; ++i){
        int len = strlen(str[i] + 1);
        for(int j = 1; j <= len; ++j) --ump[hs[i][j]];
        for(int j = 1; j <= len; ++j){
            LL suffix = calc(i,len - j + 1,len);
            if(!ump[suffix]) continue;
            int x = 1,y = 1;
            LL prefix = suffix;
            for(int k = 2; k*j <= len; ++k){
                LL suffix2 = calc(i,len - j*k + 1,len);
                prefix = (prefix*B[j] + suffix)%mod;
                if(suffix2 != prefix) break;
                if(ump[prefix]) x = k;
                y = k;
            }
            if(x == y && x == 1) continue;
            if(x == y) --x;
            if(j*(x + y) > a + b){
                a = x*j;
                b = y*j;
            }
        }
        for(int j = 1; j <= len; ++j) ump[hs[i][j]]++;
    }
    printf("%d %d
",a,b);
}
int main(){
    int kase;
    init();
    scanf("%d",&kase);
    while(kase--){
        scanf("%d",&n);
        for(int i = 0; i < n; ++i)
            scanf("%s",str[i] + 1);
        solve();
    }
    return 0;
}
/*
2
3
abcabe
defg
bcabab
*/