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遞推遞迴練習 C

#include<bits/stdc++.h>
using namespace std;
int s[35][35][35]={0};
int f(int a,int b,int c);
int main()
{ int a,b,c;
  while(cin>>a>>b>>c)
  { cout<<f(a,b,c)<<endl;
  }

int f(int a,int b,int c)

  if(a<=0||b<=0||c<=0)return 1;
  if(s[a][b][c]!=0)return s[a][b][c];
  if(a>20||b>20||c>20)return s[a][b][c]=f(20,20,20);
  if(a<b&&b<c)return s[a][b][c]=f(a,b,c-1)+f(a,b-1,c-1)-f(a,b-1,c);
  return s[a][b][c]=f(a-1,b,c)+f(a-1,b-1,c)+f(a-1,b,c-1)-f(a-1,b-1,c-1);
}