UVa - 371 Ackermann Functions DP Solution

#include<stdio.h>

#define MX 10000000

#define swap(xxx, yyy) (xxx) ^= (yyy) ^= (xxx) ^= (yyy)

unsigned long DP[MX];

unsigned long tmp,max,maxItem,k,t;

unsigned long cycleLen(unsigned long i,unsigned long n,unsigned long cnt)

{

    if(i<MX && DP[i]){ DP[n]=cnt+DP[i];return DP[n]; }

    if(i==1) { DP[n]=cnt;return DP[n]; }

    if(i%2 == 0) return cycleLen(i/2,n,cnt+1);

    return cycleLen(3*i+1,n,cnt+1);

}

unsigned long mxLen(unsigned long i,unsigned long j)

{

    if(i>j) swap(i,j);

    if(i==1){

        max=3+1;

        maxItem=1; 

    }

    else{

        max=cycleLen(i,i,0)+1;

        maxItem=i;

    }

    for(k=i+1;k<=j;k++){

        t=cycleLen(k,k,0)+1;

        if(max<t){max=t;maxItem=k;}

    }

    return max;

}

int main(){

    unsigned long a,b,mx;

//    freopen("input.txt","r",stdin);

//    freopen("output.txt","w",stdout);

    while(1)

    {

        scanf("%lu %lu",&a,&b);

        if(a==0 && b==0) break;

        mx=mxLen(a,b);

        if(a>b){swap(a,b);}

        printf("Between %lu and %lu, %lu generates the longest sequence of %lu values.\n",a,b,maxItem,mx-1);

    }

    return 0;

}