P1025 數的劃分

P1025 數的劃分

題解

時隔許久打個dfs

爲了防止重複，咱們劃分數字的時候按照升序劃分

代碼

#include<iostream>
#include<cstdio>
#include<cstdlib>
#include<algorithm>
#include<string>
#include<cstring>
#include<queue>
#include<cmath>

using namespace std;
typedef long long ll;

inline int read()
{
    int ans=0;
    char last=' ',ch=getchar();
    while(ch<'0'||ch>'9') last=ch,ch=getchar();
    while(ch>='0'&&ch<='9') ans=ans*10+ch-'0',ch=getchar();
    if(last=='-') ans=-ans;
    return ans;
}

int n,m,ans=0;

int dfs(int k,int pre,int res)
{
    int ret=0;
    if(k==m) return res==0;
    if(res<=0) return 0;
    for(int i=pre;(i+m-k-1)<=res;i++){
        ret=ret+dfs(k+1,i,res-i);
    }
    return ret;
}

int main()
{
    n=read();m=read();
    ans=dfs(0,1,n);
    printf("%d\n",ans);
    return 0;
}