poj 2352 Stars （树状数组）

题目分析：一个数组中，求某个元素左边小于等于它的数的个数，记为level,  ans[level]++,按level 从0到输出他们出现次数，

代码：

#include<iostream>#include<cstdio>#include<memory.h>using namespace std;const int MAX=100000;int ans[MAX],tree[MAX],n;int LowBit(int x){return x&(-x);}int GetSum(int x){int temp=0;for(int i=x;i>=1;i-=LowBit(i))temp+=tree[i];return temp;}void UpDate(int x,int c){for(int i=x;i<=MAX;i+=LowBit(i))        tree[i]+=c;}int main(){while(scanf("%d",&n)!=EOF){int x,y;memset(tree,0,sizeof(tree));memset(ans,0,sizeof(ans));for(int i=1;i<=n;i++){scanf("%d %d",&x,&y);                    ans[GetSum(x+1)]++;//因为0<=x<=32000，注意x==0，否则死循环UpDate(x+1,1);}for(int i=0;i<n;i++)printf("%d\n",ans[i]);}system("pause");return 0;}