poj 3264 Balanced Lineup

基础的线段树

/*
PROG:
LANG: C++11 
*/
#include <cstdio>
#include <cmath>
#include <cstring>
#include <string>
#include <cstdlib>
#include <climits>
#include <ctype.h>
#include <queue>
#include <stack>
#include <vector>
#include <utility>
#include <deque>
#include <set>
#include <map>
#include <iostream>
#include <fstream>
#include <algorithm>
#include <time.h>

using namespace std;
#define mst(a,b) memset(a,b,sizeof(a))

typedef long long ll;
typedef pair<int, int> P;
const ll MOD = 1000000007;
const int INF = 0x7fffffff;
const int MAXN = 50001;

struct node {
    int left, right, ma, mi;
} tree[MAXN*4];

int num[MAXN];

void build(int i, int l, int r){
    tree[i].left = l;
    tree[i].right = r;
    if(l == r){
        tree[i].ma = num[l];
        tree[i].mi = num[l];
        return ;
    }
    int mid = (l+r)/2;
    build(2*i, l, mid);
    build(2*i+1, mid+1, r);
    tree[i].mi = min( tree[i*2+1].mi, tree[2*i].mi);
    tree[i].ma = max( tree[i*2+1].ma, tree[2*i].ma);
}

// first is ma, second is mi
P query(int i, int l, int r){
    P ans;
    if(tree[i].left == l && tree[i].right == r){
        ans.first = tree[i].ma;
        ans.second = tree[i].mi;
        return ans;
    }
    int mid = (tree[i].left + tree[i].right)/2;
    if( r <= mid)
        ans = query(i*2, l, r);
    else if( l > mid)
        ans = query(i*2+1, l, r);
    else{
        P p1 = query(i*2, l, mid);
        P p2 = query(i*2+1, mid+1, r);
        ans.first = max(p1.first, p2.first);
        ans.second = min(p1.second, p2.second);
    }
    return ans;
}

int main()
{
    int N, Q;
    scanf("%d%d", &N, &Q);
    for(int i = 1; i <= N; i++){
        scanf("%d", &num[i]);
    }
    build(1,1,N);
    int a, b;
    for(int i = 0; i < Q; i++){
        scanf("%d%d", &a, &b);
        P pp = query(1,a,b);
        printf("%d\n", pp.first - pp.second);
    }
    return 0;
}