By yusijia

Updated:

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#include<cstdio>
#include<cstring>
#include<iostream>
#include<algorithm>
using namespace std;

#define Lson(x) (x<<1)              //左移相当于乘2；  2*n
#define Rson(x) (Lson(x)|1)         //相当于2*n + 1
#define Mid(x,y) ((x+y)>>1)         //右移相当于除2，相当于n / 2
#define Sum(x,y) (x+y)

const int N = 10;
const int MAXN = 50010;

int n, m;
int num[MAXN];
struct Node{
    int left;
    int right;
    int sum;
    int sum2;
};
Node node[MAXN << 2];                  //n个数，则线段树占4倍n的内存

void push_up(int pos){
    node[pos].sum = max(node[Lson(pos)].sum,node[Rson(pos)].sum);
    node[pos].sum2 = min(node[Lson(pos)].sum2,node[Rson(pos)].sum2);
    }

void init(int left , int right , int pos){
    node[pos].left = left;
    node[pos].right = right;

    if(left == right){              //叶子节点
       node[pos].sum = num[left];
       node[pos].sum2 = num[left];
       return;
    }

    int x = Mid(left , right);

    init(left , x , Lson(pos));     //向左节点去
    init(x+1 , right , Rson(pos));  //向右节点去
    push_up(pos);                   //回溯的时候对本节点的sum赋值(左孩子的sum+右孩子的sum)
}

int queryMax(int left , int right , int pos){
    if(node[pos].left == left && node[pos].right == right)
        return node[pos].sum;

    int x = Mid(node[pos].left , node[pos].right);

    if(right <= x)                          //在左孩子的区间里
        return queryMax(left , right , Lson(pos));
    else if(left > x)                       //在右孩子的区间里
        return queryMax(left , right , Rson(pos));
    else                                    //如果有部分在左孩子的区间和右孩子的区间里，就将其分为两个区间
        return max(queryMax(left , x , Lson(pos)), queryMax(x+1 , right , Rson(pos)));
}

int queryMin(int left , int right , int pos){
    if(node[pos].left == left && node[pos].right == right)
        return node[pos].sum2;

    int x = Mid(node[pos].left , node[pos].right);

    if(right <= x)                          //在左孩子的区间里
        return queryMin(left , right , Lson(pos));
    else if(left > x)                       //在右孩子的区间里
        return queryMin(left , right , Rson(pos));
    else                                    //如果有部分在左孩子的区间和右孩子的区间里，就将其分为两个区间
        return min(queryMin(left , x , Lson(pos)), queryMin(x+1 , right , Rson(pos)));
}

int main(){
    int q;
    while(scanf("%d%d", &n, &q) != EOF)
    {
        for(int i = 1; i <= n; i++)
            scanf("%d", &num[i]);
        init(1, n, 1);
        int left, right;
        for(int i = 0; i < q; i++){
            scanf("%d%d", &left, &right);
            printf("%d\n", queryMax(left, right, 1) - queryMin(left, right, 1));
        }
    }
    return 0;
}
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