HDU 2266 How Many Equations Can You Find
2017-03-24 12:37
381 查看
题目链接:戳这里
题意:给一个字符串,向里面添加“+”或“-”,使之结果等于N。
先自己做了一遍,结果不对,最后发现是我考虑不周全,我的搜索过程,只加上或减去了运算符之后的第一个数字,导致最后结果少了一些(见示例)。正确的方法:搜索到每一位数字时,要加上或减去它之后的所有组合情况。
最初的错误代码:
#include<string>
#include<iostream>
using namespace std;
string str;
int len,cnt;
long long n;
void DFS(int x,int sum)
{
if(x==len)
{
if(sum==n)
cnt++;
return;
}
DFS(x+1,sum+(str[x]-'0'));
DFS(x+1,sum-(str[x]-'0'));
DFS(x+1,sum*10+(str[x]-'0'));
}
int main()
{
while(cin>>str>>n)
{
len=str.length();
cnt=0;
DFS(1,(str[0]-'0'));
cout<<cnt<<endl;
}
return 0;
}
AC的代码:
#include<string>
#include<iostream>
using namespace std;
string str;
int len,cnt;
long long n;
void DFS(int x,int sum)
{
if(x==len)
{
if(sum==n)
cnt++;
return;
}
long long tmp=0;
for(int i=x;i<len;i++)
{
tmp=tmp*10+(str[i]-'0');
DFS(i+1,sum+tmp);
if(x)
DFS(i+1,sum-tmp);
}
}
int main()
{
while(cin>>str>>n)
{
len=str.length();
cnt=0;
DFS(0,0);
cout<<cnt<<endl;
}
return 0;
}
题意:给一个字符串,向里面添加“+”或“-”,使之结果等于N。
先自己做了一遍,结果不对,最后发现是我考虑不周全,我的搜索过程,只加上或减去了运算符之后的第一个数字,导致最后结果少了一些(见示例)。正确的方法:搜索到每一位数字时,要加上或减去它之后的所有组合情况。
最初的错误代码:
#include<string>
#include<iostream>
using namespace std;
string str;
int len,cnt;
long long n;
void DFS(int x,int sum)
{
if(x==len)
{
if(sum==n)
cnt++;
return;
}
DFS(x+1,sum+(str[x]-'0'));
DFS(x+1,sum-(str[x]-'0'));
DFS(x+1,sum*10+(str[x]-'0'));
}
int main()
{
while(cin>>str>>n)
{
len=str.length();
cnt=0;
DFS(1,(str[0]-'0'));
cout<<cnt<<endl;
}
return 0;
}
AC的代码:
#include<string>
#include<iostream>
using namespace std;
string str;
int len,cnt;
long long n;
void DFS(int x,int sum)
{
if(x==len)
{
if(sum==n)
cnt++;
return;
}
long long tmp=0;
for(int i=x;i<len;i++)
{
tmp=tmp*10+(str[i]-'0');
DFS(i+1,sum+tmp);
if(x)
DFS(i+1,sum-tmp);
}
}
int main()
{
while(cin>>str>>n)
{
len=str.length();
cnt=0;
DFS(0,0);
cout<<cnt<<endl;
}
return 0;
}
相关文章推荐
- HDU-2266-How Many Equations Can You Find【交叉DFS】
- hdu 2266 How Many Equations Can You Find
- hdu - 2266 How Many Equations Can You Find (简单dfs)
- HDOJ(HDU).2266 How Many Equations Can You Find (DFS)
- HDU 2266 How Many Equations Can You Find(模拟,深搜)
- 【HDU】2266 - How Many Equations Can You Find(dfs)
- 【HDU 2266 How Many Equations Can You Find】+ DFS
- HDU 2266 How Many Equations Can You Find (DFS)
- HDU 2266 How Many Equations Can You Find【dfs】
- hdu 2266(How Many Equations Can You Find)搜索、递归
- hdu2266——How Many Equations Can You Find
- hdu 2266 How Many Equations Can You Find
- HDU:2266 How Many Equations Can You Find(深搜+DFS)
- HDU 2266 How Many Equations Can You Find 深搜
- hdu 2266 How Many Equations Can You Find
- HDU 2266 How Many Equations Can You Find (技巧性dfs)
- 【HDOJ】2266 How Many Equations Can You Find
- hdoj 2266 How Many Equations Can You Find (dfs)
- 杭电2266 How Many Equations Can You Find
- HDOJ 题目2266 How Many Equations Can You Find(DFS水)