HDU1394线段树单点更新

来源：互联网发布：linux 打印内核编辑：程序博客网时间：2024/05/01 01:08

原题http://acm.hdu.edu.cn/showproblem.php?pid=1394

//先求原数列的逆序数，最后用递归来求后面的。#include <stdio.h>#include <stdlib.h>#include <malloc.h>#include <limits.h>#include <ctype.h>#include <string.h>#include <string>#include <math.h>#include <algorithm>#include <iostream>#include <stack>#include <queue>#include <deque>#include <map>#include <set>#include <vector>using namespace std;#define lson l,m,rt<<1#define rson m+1,r,rt<<1|1#define maxn 5555int SUM[maxn<<2];int min(int a,int b){if(a < b)return a;elsereturn b;} void pushup(int rt){SUM[rt] = SUM[rt<<1]+SUM[rt<<1|1];}void build(int l,int r,int rt){SUM[rt] = 0;if(l == r){return ;}int m = (l+r)>>1;build(lson);build(rson);}void update(int a,int l,int r,int rt){if(l == r){SUM[rt]++;return ;}int m = (l+r)>>1;if(a <= m){update(a,lson);}if(a > m){update(a,rson);}pushup(rt);}int query(int L,int R,int l,int r,int rt){if(L<=l && r<=R){return SUM[rt];}int m = (l+r)>>1;int ret = 0;if(L <= m){ret+=query(L,R,lson);}if(R > m){ret+=query(L,R,rson);}return ret;}int main(){int n;int i;int num[maxn];while(~scanf("%d",&n)){build(0,n-1,1);int sum = 0;for(i=0;i<n;i++){scanf("%d",&num[i]);sum+=query(num[i],n-1,0,n-1,1);update(num[i],0,n-1,1);}int ret = sum;for(i=0;i<n;i++){sum = sum+n-num[i]-1-num[i];//公式ret = min(ret,sum);}printf("%d\n",ret);}return 0;}

0 0