歷屆試題 帶分數
時間限制:1.0s 內存限制:256.0MB
直接用DFS搜索,假設n爲156,整數不會超過三位,分別搜索整數位數爲1-3三種情況下符合條件的答案,其中整數和分母搜索得出,分子計算得出,並且分子位數必須小於等於分母位數,代碼如下,速度比全排列快不少,15MS通過,全排列需要200Ms左右。
#include<iostream>
#include<cstring>
using namespace std;
int vis[10], vis1[10], ans, n;
void dfs(int t,int left, int left_number, int right, int right_number)
{
if (left >= n) return;
if(left_number==t)
{int z = (n - left)*right;
int c = 0, ok = 1;
memset(vis1, 0, sizeof(vis1));
while (z)
{
int r = z % 10;
if (vis[r] || vis1[r] || r == 0) {
ok = 0;break;
}
else
vis1[r] = 1,
c++,
z = z / 10;
}
if (ok == 1 && c + left_number + right_number == 9)
{
ans++;return;
}
}
for (int i = 1;i <= 9;i++)
if (!vis[i])
{
if (right_number==0&&left<n)
{
vis[i] = 1;
dfs(t,left * 10 + i, left_number + 1, right, right_number);
vis[i] = 0;
}
if (left_number==t&&right_number<(9 - left_number) / 2)
{
vis[i] = 1;
dfs(t,left, left_number, right * 10 + i, right_number + 1);
vis[i] = 0;
}
}
}
int main()
{
cin >> n;
int cnt=0,t=n;
while (t)
{
cnt++;
t = t / 10;
}
for (int i = 1;i <= cnt;i++)
dfs(i,0, 0, 0, 0);
cout << ans;
return 0;
}