POJ 1177 Picture

POJ_1177

    这个题目和POJ_1151基本思路是一样的，一些具体的思路可以参考我的那篇题解：http://www.cnblogs.com/staginner/archive/2012/02/20/2359396.html。

    相比算面积不同的是，每次计算面积的操作需要改为计算周长的操作，同时周长可以分成平行于x轴的部分和平行y轴的部分分开来求。

#include<stdio.h>
#include<string.h>
#include<stdlib.h>
#define zero 1e-8
#define MAXD 10010
#define INF 10010
int N, X, M;
struct square
{
    double x1, y1, x2, y2;
}s[MAXD];
double left[MAXD], right[MAXD], tx[MAXD], ty[MAXD];
int cmp1(const void *_p, const void *_q)
{
    square *p = (square *)_p, *q = (square *)_q;
    return p->y1 < q->y1 ? -1 : 1;
}
int cmp2(const void *_p, const void *_q)
{
    square *p = (square *)_p, *q = (square *)_q;
    return p->x1 < q->x1 ? -1 : 1;
}
int cmp3(const void *_p, const void *_q)
{
    double *p = (double *)_p, *q = (double *)_q;
    return *p < *q ? -1 : 1;
}
double fabs(double x)
{
    return x < 0 ? -x : x;
}
int dcmp(double x)
{
    return fabs(x) < zero ? 0 : (x < 0 ? -1 : 1);
}
void init()
{
    int i, j, k;
    X = 0;
    for(i = 0; i < N; i ++)
    {
        scanf("%lf%lf%lf%lf", &s[i].x1, &s[i].y1, &s[i].x2, &s[i].y2);
        tx[X] = s[i].x1, ty[X] = s[i].y1;
        ++ X;
        tx[X] = s[i].x2, ty[X] = s[i].y2;
        ++ X;
    }
}
void solve()
{
    int i, j, k;
    double ans = 0, up, down;
    qsort(s, N, sizeof(s[0]), cmp1);
    qsort(tx, X, sizeof(tx[0]), cmp3);
    M = 0;
    for(i = 1; i < X; i ++)
        if(dcmp(tx[i] - tx[i - 1]) != 0)
        {
            left[M] = tx[i - 1], right[M] = tx[i];
            ++ M;
        }
    for(i = 0; i < M; i ++)
    {
        up = down = -INF;
        for(j = 0; j < N; j ++)
            if(dcmp(left[i] - s[j].x1) >= 0 && dcmp(right[i] - s[j].x2) <= 0)
            {
                if(dcmp(s[j].y1 - up) > 0)
                {
                    ans += 2 * (right[i] - left[i]);
                    down = s[j].y1, up = s[j].y2;
                }
                else if(dcmp(s[j].y2 - up) > 0)
                    up = s[j].y2;
            }
    }
    qsort(s, N, sizeof(s[0]), cmp2);
    qsort(ty, X, sizeof(ty[0]), cmp3);
    M = 0;
    for(i = 1; i < X; i ++)
        if(dcmp(ty[i] - ty[i - 1]) != 0)
        {
            left[M] = ty[i - 1], right[M] = ty[i];
            ++ M;
        }
    for(i = 0; i < M; i ++)
    {
        up = down = -INF;
        for(j = 0; j < N; j ++)
            if(dcmp(left[i] - s[j].y1) >= 0 && dcmp(right[i] - s[j].y2) <= 0)
            {
                if(dcmp(s[j].x1 - up) > 0)
                {
                    ans += 2 * (right[i] - left[i]);
                    down = s[j].x1, up = s[j].x2;
                }
                else if(dcmp(s[j].x2 - up) > 0)
                    up = s[j].x2;
            }
    }
    printf("%.0lf\n", ans);
}
int main()
{
    while(scanf("%d", &N) == 1)
    {
        init();
        solve();
    }
    return 0;
}