hdu 1166 树状数组 & 线段树

//树状数组
#include "stdafx.h"
#include <iostream>
using namespace std;

const int MAXN = 50010;
int num[MAXN];
int sum[MAXN];//sum[i]: lowbit为i的二进制表示中右边第一个1所代表的数字,然后sum[i]里存的就是从num[i]开始向前数lowbit个元素之和
int n;

int lowbit(int x) //取x的最低位
{
return x&(-x);
}

void add(int i, int val)  //将第i个元素增加val
{
//i的祖先都增加val
while(i <= n)
{
sum[i] += val;
i += lowbit(i);   //将i的二进制未位1补为0得到其父亲
}
}

int Sum(int i)   //求前i项的和
{
int s = 0;
//将前i项分段
while(i > 0)
{
s += sum[i];
i -= lowbit(i);  //去掉i的二进制最后一个1
}
return s;
}

int main()
{
int t;
char order[10];
int a,b;
cin>>t;
for(int Case=1; Case<=t; Case++)
{
memset(sum,0,sizeof(sum));
cout<<"Case "<<Case<<":"<<endl;
cin>>n;
for(int i=1; i<=n; i++)
{
cin>>num[i];
add(i,num[i]);
}
while(1)
{
cin>>order;
if(strcmp(order,"End") == 0)
{
break;
}
cin>>a>>b;
if(strcmp(order,"Query") == 0)
{
cout<<Sum(b)-Sum(a-1)<<endl;
}
if(strcmp(order,"Add") == 0)
{
add(a,b);
}
if(strcmp(order,"Sub") == 0)
{
add(a,-b);
}
}
}
return 0;
}

//线段树,hdu 1166,节点更新，区间求和

#include <iostream>
using namespace std;

const int MAXN = 50000 + 100;

struct treeNode
{
int left;
int right;
int num;
}node[MAXN*3];

int num[MAXN];

int buildTree(int low, int top, int index) //功能：建树.父节点是左右子节点之和
{
node[index].left = low;
node[index].right = top;
if (low == top)                    //是否已经递归到最低层
{
node[index].num = num[low];
return node[index].num;
}
int mid = (low + top) / 2;
node[index].num = buildTree(low,mid,index*2) + buildTree(mid+1,top,index*2+1);  //父节点为左右子节点之和
return node[index].num;
}

void update(int k, int num, int index)
{
node[index].num = node[index].num + num;  //每一个覆盖的区间都加上num
if (node[index].left == node[index].right && node[index].left == k) //已经更新到最底层并且找到K点
{
return;
}
int mid = (node[index].left + node[index].right) / 2;
if (k <= mid)                //如果k在左子树中
{
update(k,num,index*2);
}
else                          //如果k在右子树中
{
update(k,num,index*2+1);
}
}

int search(int low, int top, int index)
{
if (node[index].left == low && node[index].right == top)  //找到完全重合的区间,直接返回该值，即为本次搜索的最终结果
{
return node[index].num;
}
int mid = (node[index].left + node[index].right) / 2;
if (top <= mid)      //搜索区间位于左子树
{
return search(low,top,index*2);
}
else if(low > mid)   //搜索区间位于右子树
{
return search(low,top,index*2+1);
}
else                  //搜索区间在左右子树间,即将区间分成2部分
{
return search(low,mid,index*2) + search(mid+1,top,index*2+1);
}
}

int main()
{
int t;
int n;
cin>>t;
char command[10];
int a,b;
for (int Case=1; Case<=t; Case++)
{
cin>>n;
for (int i=1; i<=n; i++)
{
cin>>num[i];
}
buildTree(1,n,1);
cout<<"Case "<<Case<<":"<<endl;
while (1)
{
cin>>command;
if(command[0] == 'E')
{
break;
}
cin>>a>>b;
if (command[0] == 'Q')
{
cout<<search(a,b,1)<<endl;
}
else if (command[0] == 'A')
{
update(a,b,1);
}
else if (command[0] == 'S')
{
update(a,-b,1);
}
}
}
return 0;
}