HDU 4886 TIANKENG’s restaurant(Ⅱ) hash+dfs

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题意：

1、找一个字符串s使得 s不是给定母串的子串

2、且s要最短

3、s在最短情况下字典序最小

hash，，，结果t掉了。。。加了个姿势怪异的hash值剪枝才过。。

#include <cstdio>#include <cstdlib>#include <map>#include <set>#include <algorithm>#include <cstring>#include <iostream>#include <vector>#include <string>#include <queue>using namespace std;#define N 1000100#define ll long long#define mod 2496764 char s[N];short h[8][mod], tim;bool f = false;bool dfs(ll top, ll siz, ll dep) {    if (siz > 1000000) return false;    if(top == dep)    {        for(ll i = 0; i < 8; i++)        {            if(h[top][siz * 8 + i] != tim)            {                s[top] = i + 'A';                s[top+1] = 0;                f = true;                return true;            }        }        return false;    }    for(ll i = 0; i < 8; i++)    {        s[top] = i + 'A';        if(dfs(top+1, siz * 8 + i, dep))return true;    }    return false;}int main(){    int i, j, T; scanf("%d",&T);    tim = 0;    while(T--) {        tim ++;        scanf("%s", s);        f = false;        for(i = 0; s[i]; i++)        {            ll ans = 0;            for(j = 0; j < 7 && s[i+j]; j++)            {                ans = ans * 8 + s[i + j] - 'A';                h[j][ans] = tim;            }        }       for(i = 0; i < 8; i++)            if(dfs(0, 0, i))break;        puts(s);    }    return 0;}

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