poj2155 Matrix 【二維樹狀數組】

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有工具在手，這題就是一個模板題，就是有點不清楚，最後問的是單個元素的值，它怎麼sum求出來的

#include <iostream>#include <cstdlib>#include <cstring>#include <cstdio>using namespace std;#define maxn 1005int c[maxn][maxn];int Row, Col;inline int Lowbit(const int &x){    return x & (-x);}int Sum(int i, int j){    int tempj, sum = 0;    while (i > 0)    {        tempj = j;        while (tempj > 0)        {            sum += c[i][tempj];            tempj -= Lowbit(tempj);        }        i -= Lowbit(i);    }    return sum;}void Update(int i, int j, int num){    int tempj;    while (i <= Row)    {        tempj = j;        while (tempj <= Col)        {            c[i][tempj] += num;            tempj += Lowbit(tempj);        }        i += Lowbit(i);    }}int main(){    #ifndef ONLINE_JUDGEfreopen("G:/1.txt","r",stdin);freopen("G:/2.txt","w",stdout);#endif    int T;scanf("%d",&T);while(T--){    memset(c,0,sizeof(c));int N,Q;scanf("%d%d",&N,&Q);getchar();Row=N;Col=N;for(int i=1;i<=Q;i++){char ques;int a,b,c,d;scanf("%c ",&ques);//getchar();if(ques=='C'){scanf("%d%d%d%d",&a,&b,&c,&d);getchar();c++;d++;Update(a,b,1);Update(c,d,1);Update(c,b,-1);Update(a,d,-1);}else if(ques=='Q'){scanf("%d%d",&a,&b);getchar();printf("%d\n",1&Sum(a,b));}}printf("\n");}}