POJ 1788

求多边形周长。角都是直角。

#include <iostream>
#include <cstring>
#include <cstdio>
#include <cstdlib>
#include <algorithm>

#define N 222222

using namespace std;

struct PO
{
    int x,y;
}p[N];

int n;

inline bool cmpx(const PO &a,const PO &b)
{
    if(a.x==b.x) return a.y<b.y;
    return a.x<b.x;
}

inline bool cmpy(const PO &a,const PO &b)
{
    if(a.y==b.y) return a.x<b.x;
    return a.y<b.y;
}

inline void read()
{
    for(int i=1;i<=n;i++) scanf("%d%d",&p[i].x,&p[i].y);
}

inline void go()
{
    int ans=0;
    sort(p+1,p+1+n,cmpx);
    for(int i=1;i<=n;i+=2) ans+=p[i+1].y-p[i].y;
    sort(p+1,p+1+n,cmpy);
    for(int i=1;i<=n;i+=2) ans+=p[i+1].x-p[i].x;
    printf("The length of the fence will be %d units.\n",ans);
}

int main()
{
    while(scanf("%d",&n),n) read(),go();
    return 0;
}