子序列和问题无分析

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#include<stdio.h>#include<iostream>#include<stdlib.h>const int MAX_L  =  101;int f[MAX_L];bool used[MAX_L];int N;int ans;int init(){scanf("%d",&N);}int dfs(int step,int first){if(step>N) {ans++;return 0;}int i;for(i=first;i<=N;i++)if(!used[i]){used[i]=true;if (step<N)dfs(step+1,i+1);dfs(step+1,1);used[i]=false;//dfs}}int put(){printf("%d",ans);}int main(){freopen("bhi.in","r",stdin);freopen("bhi.out","w",stdout);init();dfs(1,1);put();return 0;}

#include<stdio.h>#include<iostream>#include<stdlib.h>const int MAX_L  =  101;int f[MAX_L];int C[MAX_L][MAX_L];int N;int c(int n,int m){if (m==0||m==n) return 1;if (C[n][m]) return C[n][m];return C[n][m] = c(n-1,m-1)+c(n-1,m);}int init(){scanf("%d",&N);}int work(){int i,j;f[0]=1;f[1]=1;for(i=2;i<=N;i++) //dpfor(j=1;j<=i;j++)f[i]+=c(i,j)*f[i-j];}int put(){printf("%d",f[N]);}int main(){freopen("bhi.in","r",stdin);freopen("bhi.out","w",stdout);init();work();put();return 0;}

#include<stdio.h>#include<iostream>#include<memory.h>const int MAX_L  =  101;int f[MAX_L];bool used[MAX_L];int N;int ans;int init(){scanf("%d",&N);memset(f,-1,sizeof(f));}int dfs(int step,int first){if(step>N) {ans++;return 0;}int i;for(i=first;i<=N;i++)if(!used[i]){used[i]=true;if (step<N)dfs(step+1,i+1);if (f[N-step]==-1){f[N-step]=ans;dfs(step+1,1);f[N-step]=ans-f[N-step];}else ans+=f[N-step];used[i]=false;}}int put(){printf("%d",ans);}int main(){freopen("bhi.in","r",stdin);freopen("bhi.out","w",stdout);init();dfs(1,1);put();return 0;}

子序列和问题 无分析

子序列和问题无分析