poj-3067

来源：互联网发布：linux中打开一个文件编辑：程序博客网时间：2024/05/30 02:53

与2299类似，求逆序数；

首先按x升序排列，再求y的逆序数；

#include <iostream>#include <stdio.h>#include <string.h>#include <algorithm>#include <stdlib.h>using namespace std;int b[1000005];int n,m,k;struct q{    int x;    int y;}p[1000105];bool cmp(q a ,q b){    if (a.x != b.x)        return a.x < b.x;    else        return a.y <= b.y;}int lowbit(int i){    return i&-i;}int sum(int i){    long long  ans =0;    while (i>0)    {        ans += b[i];        i -= lowbit(i);    }    return ans;}void update(int i,int v){    while (i<=m)    {        b[i]+=v;        i+=lowbit(i);    }}int main (){    int t ;    int ss=1;    scanf ("%d",&t);    while (t--)    {        scanf ("%d%d%d",&n,&m,&k);        for (int i=1;i<=k;i++)        {            scanf ("%d%d",&p[i].x,&p[i].y  );        }        sort (p+1,p+1+k,cmp);        memset(b,0,sizeof(b));        long long  ans =0 ;        for (int i=1;i<=k;i++)        {            update(p[i].y,1);            ans += i-sum( p[i].y );        }        printf("Test case %d: ",ss++);        printf("%lld\n",ans);    }    return 0;}

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