Here you will find solutions of many problems on spoj. If you want solution of some problem which is not listed in blog or have doubt regarding any spoj problem (which i have solved) or any programming concept (data structure) you can mail me @ raj.nishant360@gmail.com
And my humble request to you all that don't copy the code only try to understand the logic and algorithm behind the code. I have started this because if you tried as hard as you can and still can't find any solution to the problem then you can refer to this.
You can read my answer how to start competitive programming CLICK HERE

Saturday, August 23, 2014

Segment tree GSS3 & GSS1

First of all read about segment tree and it basic functioning. You can read it from HERE .

Given below code is for GSS3 & GSS1 spoj .

Here i have implemented segment tree as given in above link.



//for GSS1 remove update part from main function

#include <bits/stdc++.h>
using namespace std;
#define INT -1000000
int k;
struct node
{
    int result,pre,suf,sum;
    void split(node &a , node &b){}
    void merge(node a , node b)
    {
        sum = a.sum + b.sum;
        pre = max(a.pre , (a.sum + b.pre));
        suf = max(b.suf , (b.sum + a.suf));
        result = max(a.suf + b.pre,max(a.result , b.result));
    }
    node()
    {
        result = pre = suf = sum = INT;
    }
    node(int temp)
    {
        result = pre = suf = sum = temp;
    }
}tree[131080];
void update(int pos)
{
    pos>>=1;
    while(pos!=0)
    {
        tree[pos].merge(tree[pos*2],tree[pos*2 + 1]);
        pos>>=1;
    }
}
node range_query(int root , int left_most , int right_most , int l ,int r)
{
    if( l <= left_most && r >= right_most )
        return tree[root];

    int l_child = (root<<1) , r_child = l_child + 1 , mid = (left_most + right_most )>>1 ;

    tree[root].split(tree[l_child],tree[r_child]);

    node l_node = node() , r_node = node();

    if(l <= mid)
        l_node = range_query(l_child , left_most , mid , l , r);
    if(r > mid)
        r_node = range_query(r_child , mid + 1 , right_most, l , r);

    tree[root].merge(tree[l_child] , tree[r_child]);

    node temp = node();
    temp.merge(l_node,r_node);

    return temp;
}
int main()
{
    int n,temp,l,r;
    scanf("%d",&n);
    k = ceil(log(n)/log(2));
    int pos = (1<<k);
    int a[n];
    for(int i=0;i<n;i++){
        scanf("%d",&temp);
        tree[pos+i] = node(temp);
        update(pos+i);
    }
    int m,c;

    scanf("%d",&m);
    while(m--)
    {
        scanf("%d%d%d",&c,&l,&r);
        if(c==1)
            printf("%d\n",(range_query(1,1,pos,l,r)).result);
        else if(c==0)// Update part-> remove this condition for GSS1.
        {
            tree[pos+l-1] = node(r);
            update(pos + l -1);
        }
    }
    return 0;
}