Squares

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题意：给出n个正方形，问最远的两个点距离多少
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解法：旋转卡壳，计算二维平面最远的两个点
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#include <cstdio>#include <algorithm>using namespace std;struct Point {    int x, y;    Point(int _x = 0, int _y = 0) {        x = _x; y = _y;    }    Point operator -(const Point &b) {        return Point(x - b.x, y - b.y);    }    int operator ^(const Point &b) const {        return x*b.y-y*b.x;    }    int operator *(const Point &b) const {        return x * b.x + y * b.y;    }};int dist2(Point a, Point b) {    return (a-b) * (a-b);}const int MAXN = 400010;Point list[MAXN];int Stack[MAXN], top;bool _cmp(Point p1, Point p2){    int tmp = (p1-list[0]) ^ (p2-list[0]);    if (tmp > 0) return true;    else if (tmp == 0 && dist2(p1, list[0]) <= dist2(p2, list[0]))    {        return true;    }    return false;}void Graham(int n){    Point p0;    int k = 0;    p0 = list[0];    for (int i = 1; i < n; i++)        if (p0.y > list[i].y || (p0.y == list[i].y && p0.x > list[i].x))        {            p0 = list[i]; k = i;        }    Point tmp = list[0]; list[0] = list[k]; list[k] = tmp;    sort(list+1, list+n, _cmp);    if (n==1)    {        top = 1; Stack[0] = 0; return;    }    if (n == 2)    {        top = 2; Stack[0] = 0; Stack[1] = 1; return;    }    Stack[0] == 0; Stack[1] = 1;    top = 2;    for (int i = 2; i < n; i++)    {        while (top > 1 && ((list[Stack[top-1]] - list[Stack[top-2]]) ^ (list[i] - list[Stack[top-2]])) <= 0)            top--;        Stack[top++] = i;    }}int rotating_calipers(Point p[], int n){    int ans = 0;    Point v;    int cur = 1;    for (int i = 0; i < n; i++)    {        v = p[i] - p[(i + 1) % n];        while ((v^(p[(cur+1)%n]-p[cur])) < 0) cur = (cur + 1) % n;        ans = max(ans,max(dist2(p[i], p[cur]), dist2(p[(i+1)%n], p[(cur+1) % n])));    }    return ans;}Point p[MAXN];int main(){    int t, n, rr;    scanf("%d", &t);    while (t--)    {        scanf("%d", &n);        for (int i = 0; i < n; i++)        {            scanf("%d %d %d", &list[i * 4].x, &list[i * 4].y, &rr);            list[(i*4+1)].x = list[i*4].x + rr; list[(i*4+1)].y = list[i*4].y + rr;            list[(i*4+2)].x = list[i*4].x; list[(i*4+2)].y = list[i*4].y + rr;            list[(i*4+3)].x = list[i*4].x + rr; list[(i*4+3)].y = list[i*4].y;        }        Graham(n*4);        for (int i = 0; i < top; i++) {            p[i] = list[Stack[i]];        }        printf("%d\n", rotating_calipers(p, top));    }}