线段树实现

#include<iostream>
using namespace std;

#define max_len 1000

void build_tree(int arr[],int tree[],int node,int start,int end){
    if(start==end){
        tree[node]=arr[start];
        return;
    }
    int mid=start+(end-start)/2;
    int left_node=node*2+1;
    int right_node=node*2+2;
    build_tree(arr,tree,left_node,start,mid);
    build_tree(arr,tree,right_node,mid+1,end);
    tree[node]=tree[left_node]+tree[right_node];
}

void update_tree(int arr[],int tree[],int node,int start,int end,int idx,int val){

    if(start==end){
        arr[idx]=val;
        tree[node]=val;
        return;
    }
    int mid=start+(end-start)/2;
    int left_node=node*2+1;
    int right_node=node*2+2;
    if(idx>=start&&idx<=mid){
        update_tree(arr,tree,left_node,start,mid,idx,val);
    }else{
        update_tree(arr,tree,left_node,mid+1,end,idx,val);
    }
    tree[node]=tree[left_node]+tree[right_node];
}

int query_tree(int arr[],int tree[],int node,int start,int end,int L,int R){
    if(start>R||end<L)return 0;
    else if(start>=L&&end<=R)return tree[node];

    int mid=start+(end-start)/2;
    int left_node=2*node+1;
    int right_node=2*node+2;
    int sum_left= query_tree(arr,tree,left_node,start,mid,L,R);
    int sum_right= query_tree(arr,tree,right_node,mid+1,end,L,R);
    return sum_left+sum_right;
}
int main(){
    int arr[]={1,3,5,7,9,11};
    int size=6;
    int tree[max_len]={0};
    build_tree(arr,tree,0,0,size-1);
    return 0;
}