标签：des style color os io for ar art
Description
3 1 2 4
4 3 6
7 9
16
Behind FJ‘s back, the cows have started playing a more difficult game, in which they try to determine the starting sequence from only the final total and the number N. Unfortunately, the game is a bit above FJ‘s mental arithmetic capabilities. Input
Output
Sample Input
4 16
Sample Output
3 1 2 4
强大的STL,我比赛的时候是DFS做的。
题意：1~n排列操作的值为sum.
next_permutation的用法:按字典序输出全排列，没有返回false。
#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<limits.h>
typedef long long LL;
using namespace std;
int a[15],f[15];
int n,sum;
int solve()
{
int s=0;
for(int i=0;i<n;i++)
s+=f[i]*a[i];
return s;
}
int main()
{
while(~scanf("%d%d",&n,&sum))
{
for(int i=0;i<n;i++)
a[i]=i+1;
memset(f,0,sizeof(f));
f[0]=1;
for(int i=1;i<n;i++)
{
for(int j=i;j>=1;j--)
f[j]+=f[j-1];//杨辉三角
}
while(solve()!=sum)
next_permutation(a,a+n);
for(int i=0;i<n;i++)
printf(i==n-1?"%d\n":"%d ",a[i]);
}
return 0;
}
DFS版：
#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<limits.h>
#include<cmath>
typedef long long LL;
using namespace std;
int num[15],a[15];
int visit[15],p[15];
int n,sum,flag;
int solve(int k)
{
for(int i=1;i<=n;i++)
p[i]=num[i];
while(k>1)
{
for(int i=1;i<k;i++)
p[i]=p[i]+p[i+1];
k--;
}
return p[1];
}
void dfs(int k,int s)
{
if(s==n+1)
{
if(solve(n)==sum)
{
for(int i=1;i<=n;i++)
printf(i==n?"%d\n":"%d ",num[i]);
flag=1;
return ;
}
}
if(flag)
return ;
for(int i=1;i<=n;i++)
{
if(!visit[i])
{
visit[i]=1;
num[s]=a[i];
dfs(i,s+1);
visit[i]=0;
}
}
}
int main()
{
while(~scanf("%d%d",&n,&sum))
{
for(int i=1;i<=n;i++)
a[i]=i;
memset(visit,0,sizeof(visit));
memset(num,0,sizeof(num));
flag=0;
dfs(1,1);
}
return 0;
}
POJ 1146:
#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<limits.h>
typedef long long LL;
using namespace std;
int main()
{
int len;
char s[51];
while(scanf("%s",s)!=EOF)
{
if(s[0]=='#')
break;
len=strlen(s);
if(next_permutation(s,s+len))
printf("%s\n",s);
else
printf("No Successor\n");
}
return 0;
}
#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<limits.h>
typedef long long LL;
using namespace std;
char str[220];
int main()
{
while(~scanf("%s",str))
{
int len=strlen(str);
sort(str,str+len);
do{
printf("%s\n",str);
}while(next_permutation(str,str+len));
}
return 0;
}
POJ 3187 Backward Digit Sums(next_permutation),布布扣,bubuko.com
POJ 3187 Backward Digit Sums(next_permutation)
标签：des style color os io for ar art
原文地址：http://blog.csdn.net/u013582254/article/details/38701383
