Poj 1195 Mobile phones 题解

本题是二维树状数组的典型应用：

代码：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

using namespace std;

int c[1030][1030];
int order;
int s;

int lowbit(int t)
{
    return t&(-t);
}

void update(int x,int y,int a)
{
    while(x<=s)
    {
        int  tempy = y;
        while(tempy<=s)
        {
            c[x][tempy]+=a;
            tempy+=lowbit(tempy);
        }
        x+=lowbit(x);
    }
}

int getSum(int x,int y)
{
    int sum = 0;
    while(x>0)
    {
        int tempy = y;
        while(tempy>0)
        {
            sum+=c[x][tempy];
            tempy-=lowbit(tempy);
        }
        x-=lowbit(x);
    }
    return sum;
}

int main()
{

    scanf("%d",&order);
    while(order<3)
    {
        if(order == 0)
        {
            scanf("%d",&s);
             memset(c,0,sizeof(c));
        }
        else if(order == 1)
        {
            int x,y,a;
            scanf("%d%d%d",&x,&y,&a);
            update(x+1,y+1,a);
        }
        else if(order == 2)
        {
            int x1,x2,y1,y2;
            scanf("%d%d%d%d",&x1,&y1,&x2,&y2);
            printf("%d\n",getSum(x2+1,y2+1)-getSum(x1,y2+1)-getSum(x2+1,y1)+getSum(x1,y1));
        }
        scanf("%d",&order);
    }
    return 0;
}