POJ 1654 Area 凸包面积

水题直接码...

/********************* Template ************************/
#include <set>
#include <map>
#include <list>
#include <cmath>
#include <ctime>
#include <deque>
#include <queue>
#include <stack>
#include <bitset>
#include <cstdio>
#include <string>
#include <vector>
#include <cassert>
#include <cstdlib>
#include <cstring>
#include <sstream>
#include <fstream>
#include <numeric>
#include <iomanip>
#include <iostream>
#include <algorithm>
#include <functional>
using namespace std;

#define EPS         1e-8
#define MAXN        (int)1e5+50
#define MOD         (int)1e9+7
#define PI          acos(-1.0)
#define LINF        ((1LL)<<50)
#define INF         (1<<30);
#define max(a,b)    ((a) > (b) ? (a) : (b))
#define min(a,b)    ((a) < (b) ? (a) : (b))
#define max3(a,b,c) (max(max(a,b),c))
#define min3(a,b,c) (min(min(a,b),c))
#define BUG         cout<<"BUG! "<<endl
#define LINE        cout<<"--------------"<<endl
#define L(t)        (t << 1)
#define R(t)        (t << 1 | 1)
#define Mid(a,b)    ((a + b) >> 1)
#define lowbit(a)   (a & -a)
#define FIN         freopen("in.txt","r",stdin)
#define FOUT        freopen("out.txt","w",stdout)
#pragma comment     (linker,"/STACK:102400000,102400000")

// typedef long long LL;
// typedef unsigned long long ULL;
typedef __int64 LL;
// typedef unisigned __int64 ULL;
// int gcd(int a,int b){ return b?gcd(b,a%b):a; }
// int lcm(int a,int b){ return a*b/gcd(a,b); }

/*********************   F   ************************/
struct POINT{
    double x,y;
    POINT(double _x = 0, double _y = 0):x(_x),y(_y){};
    void show(){
        cout<<x<<" "<<y<<endl;
    }
}p[MAXN];
double dist(POINT p1,POINT p2){
    return(sqrt((p1.x-p2.x) * (p1.x-p2.x) + (p1.y-p2.y) * (p1.y-p2.y)));
}
double multiply(POINT sp,POINT ep,POINT op){
    return (sp.x-op.x) * (ep.y-op.y) - (ep.x-op.x) * (sp.y-op.y);
}
bool ptcmp(POINT a,POINT b){
    if(multiply(a,b,p[0]) == 0) return dist(p[0],a) < dist(p[0],b);
    return (multiply(a,b,p[0]) > 0);
}
double Triangle_area(POINT a,POINT b,POINT c){
    return multiply(a,b,c)/2;
}
char a[1000005];
double ax[10] = {0,-1,0,1,-1,0,1,-1,0,1};
double ay[10] = {0,-1,-1,-1,0,0,0,1,1,1};
int main()
{
    //FIN;
    //FOUT;
    int T;
    scanf("%d",&T);
    getchar();
    while(T--){
        gets(a);
        int len = strlen(a);
        double ans = 0;
        POINT st = POINT(0,0);
        for(int i = 0 ; i < len-2 ; i++){
            POINT st1 = POINT(st.x+ax[a[i]-'0'],st.y+ay[a[i]-'0']);
            POINT st2 = POINT(st1.x+ax[a[i+1]-'0'],st1.y+ay[a[i+1]-'0']);
            ans += Triangle_area(POINT(0,0),st1,st2);
            st = st1;
        }
        ans = fabs(ans);
        printf("%I64d",LL(ans));
        if((ans - floor(ans)) >= EPS)
            printf(".5\n");
        else printf("\n");
    }
    return 0;
}