poj3264

基础线段树

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//poj3264

#include <iostream>

#include <algorithm>

#include <numeric>

using namespace std;



const    int        maxn = 50002;



struct cnode

{

    int        l, r, nmin, nmax;

    cnode    *pleft, *pright;

};



int        ncount, cow[maxn], n, q, ansmax, ansmin;

cnode    tree[maxn * 2];



void init()

{

    scanf("%d%d",&n,&q);

    ncount = 0;

}



void buildtree(cnode *pnow, int start, int end)

{

    int        mid;



    pnow -> l = start;

    pnow -> r = end;

    pnow -> nmin = 1000001;

    pnow -> nmax = -1;

    mid = (start + end) / 2;

    if (start != end)

    {

        ncount++;

        pnow -> pleft = tree + ncount;

        ncount++;

        pnow -> pright = tree + ncount;

        buildtree(pnow -> pleft, start, mid);

        buildtree(pnow -> pright, mid + 1, end);

    }

}



void insert(cnode *proot, int i, int v)

{

    int        mid;



    if (proot -> l == i && proot -> r == i)

    {

        proot -> nmin = v;

        proot -> nmax = v;

        return;

    }

    proot -> nmin = _cpp_min(v, proot -> nmin);

    proot -> nmax = _cpp_max(v, proot -> nmax);

    mid = (proot -> l + proot -> r) / 2;

    if (i <= mid)

        insert(proot -> pleft, i, v);

    else

        insert(proot -> pright, i, v);

}



void query(cnode *proot, int start, int end)

{

    int        mid;



//    if (proot -> nmin >= ansmin && proot -> nmax <= ansmax)

//        return;

    if (proot -> l == start && proot -> r == end)

    {

        ansmin = _cpp_min(proot -> nmin, ansmin);    

        ansmax = _cpp_max(proot -> nmax, ansmax);

        return;

    }

    mid = (proot -> l + proot -> r) / 2;

    if (end <= mid)

        query(proot -> pleft, start, end);

    else if (start > mid)

        query(proot -> pright, start, end);

    else

    {

        query(proot -> pleft, start, mid);

        query(proot -> pright, mid + 1, end);

    }

}



int main()

{

    int        i, t, u;



    //freopen("t.txt", "r", stdin);

    init();

    buildtree(tree, 0, n - 1);

    for (i = 0; i < n; i++)

    {

        scanf("%d", &t);

        insert(tree, i, t);

    }

    for (i = 0; i < q; i++)

    {

        ansmin = 1000001;

        ansmax = -1;

        scanf("%d%d", &t, &u);

        query(tree, t - 1, u - 1);

        cout << ansmax - ansmin << endl;

    }

    return 0;

}