1 #include <iostream>
 2 #include <stdio.h>
 3
 4 using namespace std;
 5
 6 int input(int*,int*,int);    ///输入数据
 7 int calStageSum(int*,int);    ///计算树状数组
 8 int getSum(int*,int);    ///求出前n个数字的和
 9 int updataElement(int*,int*,int,int,int);    ///更新某一位置上的元素
10
11 int main (){
12     int n;
13     int newValue;
14     cout<<"Input the n(n>3) :";
15     cin>>n;
16
17     int *num = new int[n+1];
18     int *sum = new int[n+1];
19
20     cout<<"Input "<<n<<" numbers"<<endl;
21     input(num,sum,n);
22     calStageSum(sum,n);
23
24     cout<<"The sum of first three number:"<<getSum(sum,3)<<endl;
25
26     cout<<"Update the 2nd number value:";
27     cin>>newValue;
28     updataElement(sum,num,n,2,newValue);
29
30     cout<<"The sum of first three number:"<<getSum(sum,3)<<endl;
31
32     delete []num;
33     delete []sum;
34     return 0;
35 }
36
37 int input(int* num,int *sum,int n){
38     for(int i=1;i<=n;i++){
39         cin>>num[i];
40         sum[i] = num[i];
41     }
42     return 0;
43 }
44
45 int calStageSum(int *sum,int n){
46     int lowbit;
47     int par;
48     for(int i=1;i<=n;i++){
49         lowbit = ((i-1)^i)&i;
50         par = lowbit+i;   ///后继节点id
51         if(par <= n){
52             sum[par] = sum[par] + sum[i];
53         }
54     }
55     return 0;
56 }
57
58 int getSum(int* sum,int n){
59     int sumPreN = 0;
60     int lowbit  = 0;
61     while(n!=0){
62         sumPreN += sum[n];
63         lowbit = ((n-1)^n)&n;
64         n = n - lowbit; ///前驱节点id
65     }
66     return sumPreN;
67 }
68
69 int updataElement(int* sum,int *num,int n,int pos,int newvalue){
70     int lowbit = 0;
71     int dis = newvalue - num[pos];
72     num[pos] = newvalue;
73     sum[pos] = sum[pos]+dis;
74
75     while(true){
76         lowbit = ((pos-1)^pos)&pos;
77         pos = pos + lowbit; ///后继节点id
78         if(pos <= n){
79             sum[pos] = sum[pos]+dis;
80         }
81         else
82             break;
83     }
84     return 0;
85 }