|Hdu 1542|线段树|Atlantis

Hdu传送门
线段树离散化以后进行扫描线。
http://www.cnblogs.com/scau20110726/archive/2013/03/21/2972808.html
这篇文章讲得很好，详解看以上网站

#include<cstdio>  #include<algorithm>  #include<cstring>  #include<vector>#define ms(i,j) memset(i,j, sizeof i);using namespace std;const int MAXN = 100 + 5;struct xian{    int f; //up or down, up is -1, down is 1    double l, r;//the interval's end points    double h;//height    bool operator < (const xian &b) const    {        return h<b.h;    }}a[MAXN*2];double hashs[MAXN*2];//the hashsed pointsint n; #define lc o*2#define rc o*2+1#define M (l+r)/2struct st{    int col[MAXN*4*4];//col[i]>0 means this inerval was full marked    double sum[MAXN*4*4];//available room    void pushup(int o, int l, int r)    {        if (col[o]>0)        {            sum[o] = hashs[r+1]-hashs[l];        } else if (l==r) sum[o] = 0;        else {            sum[o] = sum[lc] + sum[rc];        }    }    void update(int o, int l ,int r, int x, int y, int c)    {        if (x<=l&&r<=y)        {            col[o] += c;            pushup(o,l,r);            return ;        }        if (x<=M) update(lc,l,M,x,y,c);        if (M<y) update(rc,M+1,r,x,y,c);         pushup(o,l,r);    }}tree;//binary-search the elements in hashs[]int find(int x, int y, double v){    int l = x, r = y, mid;    while (l<r)    {        mid = (l+r)/2;        if (v>hashs[mid])        {            l = mid+1;        } else r = mid;    }    return r;}int main()  {      int kase = 0;    while (scanf("%d", &n)==1&&n)    {        kase++;        for (int i=0;i<n;i++)        {            double x1, y1, x2, y2;            scanf("%lf%lf%lf%lf", &x1,&y1,&x2,&y2);            a[i*2].f = 1; a[i*2+1].f = -1;            a[i*2].l = x1; a[i*2+1].l = x1;            a[i*2].r = x2; a[i*2+1].r = x2;            a[i*2].h = y1; a[i*2+1].h = y2;//add xian             hashs[i*2] = x1; hashs[i*2+1] = x2;//add hashs        }         sort(hashs, hashs+2*n); sort(a, a+2*n); //sort to hashs        //delete the repeated elements        int m = 1;        for (int i=1;i<2*n;i++)        if (hashs[i]!=hashs[i-1]) hashs[m++] = hashs[i];         //produce        ms(tree.col, 0);        double ans = 0;        for (int i=0;i<n*2;i++)        {            int l = find(0, m, a[i].l);            int r = find(0, m, a[i].r)-1;            /*int l = lower_bound(hashs, hashs+m, a[i].l)-hashs;            int r = lower_bound(hashs, hashs+m, a[i].r)-hashs-1;*/            if (r>=l) tree.update(1,0,m-2,l,r,a[i].f);//一定要r>=l,这里原来错了             ans += (a[i+1].h-a[i].h)*tree.sum[1];        }        printf("Test case #%d\nTotal explored area: %.2f\n\n", kase, ans);    }       return 0;  }