HDU 1166

敌兵布阵，线段树，N个阵营，每个阵营会增加或者减少m个士兵，查询的时候要查询任意区间里的士兵数量

AC代码：

#include <stdio.h>
#include <string.h>
#include <algorithm>
using namespace std;

int a[50001];

struct node
{
    int left,right,sum;
} b[150005];

int Query(int left,int right,int i)
{
    int mid;
    if(b[i].left==left&&b[i].right==right)
    {
        return b[i].sum;
    }
    mid=(b[i].left+b[i].right)/2;
    if(right<=mid)
    {
        return Query(left,right,2*i);
    }
    else if(left>mid)
    {
        return Query(left,right,2*i+1);
    }
    else
    {
        return Query(left,mid,2*i)+Query(mid+1,right,2*i+1);
    }
}
void Add(int j,int num,int i)
{
    if(b[i].left==b[i].right)
    {
        b[i].sum+=num;
        return ;
    }
    else
    {
        b[i].sum+=num;
        if(j<=b[2*i].right)
        {
            Add(j,num,2*i);
        }
        else
        {
            Add(j,num,2*i+1);
        }
    }
}
void Build(int left,int right,int i){//建树
  int mid;
  b[i].left=left;
  b[i].right=right;
  if(left==right){//先用数组存下该队的人
    b[i].sum=a[left];
    return ;
  }
  //cout<<"ok"<<endl;
  mid=(left+right)/2;
  Build(left,mid,2*i);//递归建立左子树
  Build(mid+1,right,2*i+1);//递归建立右子树
  b[i].sum=b[2*i].sum+b[2*i+1].sum;//记录该结点左右子树的值
}
int main()
{
    int T,n,k,j,num;
    char s[10];
    scanf("%d",&T);
    k=0;
    while(T--)
    {
        scanf("%d",&n);
        for(int i=1; i<=n; i++)
        {
            scanf("%d",&a[i]);
        }
        printf("Case %d:
",++k);
        Build(1,n,1);
        while(1)
        {
            scanf("%s",s);
            if(!strcmp(s,"End"))
            {
                break;
            }
            scanf("%d%d",&j,&num);
            if(!strcmp(s,"Query"))
            {
                printf("%d
",Query(j,num,1));
            }
            else if(!strcmp(s,"Add"))
            {
                Add(j,num,1);
            }
            else if(!strcmp(s,"Sub"))
            {
                Add(j,-num,1);
            }
        }
    }
    return 0;
}