#include <iostream>
#include <queue>
#include<cstring>
using namespace std;
#define MAX_N 9999 + 16
int prime[MAX_N]; // 第i个素数
bool is_prime[MAX_N + 1]; //is_prime[i]为真的时候表示i为素数
int sieve(const int& n)
{
int p = 0;
fill(is_prime, is_prime + n + 1, true);
is_prime[0] = is_prime[1] = false;
for (int i = 2; i <= n; ++i)
{
if (is_prime[i])
{
prime[p++] = i;
for (int j = 2 * i; j <= n; j += i)
{
is_prime[j] = false;
}
}
}
return p;
}
int dp[MAX_N];
// 将number的倒数第digit位改成change
int get_next(int number, int digit, int change)
{
switch (digit)
{
case 0:
return number / 10 * 10 + change;
case 1:
return number / 100 * 100 + number % 10 + change * 10;
case 2:
return number / 1000 * 1000 + number % 100 + change * 100;
case 3:
return number % 1000 + change * 1000;
}
return 0;
}
int main()
{
// 先做一份素数表
sieve(MAX_N);
int N;
cin >> N;
while (N--)
{
int from, to;
cin >> from >> to;
// dfs
memset(dp, 0x3f, sizeof(dp));
dp[from] = 0;
queue<int> q;
q.push(from);
while (q.size())
{
const int current = q.front(); q.pop();
for (int i = 0; i < 4; ++i)
{
for (int j = 0; j < 10; ++j)
{
if (i == 3 && j == 0)
{
// 将第一位改成0是无意义的
continue;
}
int next = get_next(current, i, j);
if (is_prime[next] == false || dp[next] <= dp[current])
{
// 不是素数不行,如果到next已经有更小的那也不用这个变换路径了
continue;
}
dp[next] = dp[current] + 1;
q.push(next);
}
}
}
cout << dp[to] << endl;
}
}
POJ3126 搜索
猜你喜欢
转载自blog.csdn.net/hanker99/article/details/88097751
今日推荐
周排行