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53 lines
1.7 KiB
C++
53 lines
1.7 KiB
C++
#include <cstdio>
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#include <algorithm>
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inline int max(int a, int b) { return a > b ? a : b; }
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const int N = 50005;
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struct point
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{
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int x, y;
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point() {}
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point(int _x, int _y) : x(_x), y(_y) {}
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}a[N], stk[N];
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#define pArg(x) const point &x
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inline point operator+(pArg(l), pArg(r)) { return point(l.x + r.x, l.y + r.y); }
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inline point operator-(pArg(l), pArg(r)) { return point(l.x - r.x, l.y - r.y); }
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inline int cross(pArg(l), pArg(r)) { return l.x * r.y - l.y * r.x; }
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inline int dot(pArg(l), pArg(r)) { return l.x * r.x + l.y * r.y; }
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inline int len2(pArg(p)) { return p.x * p.x + p.y * p.y; }
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inline bool cmp1(pArg(l), pArg(r)) { return l.x < r.x || (l.x == r.x && l.y < r.y); }
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inline bool cmp2(pArg(l), pArg(r))
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{
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int det = cross(l - a[0], r - a[0]);
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return det != 0 ? det > 0 : len2(l - a[0]) < len2(r - a[0]);
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}
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#define nxt(x) ((x) == n - 1 ? 0 : (x) + 1)
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#define area(p, u, v) cross(u - p, v - p)
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int main()
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{
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int n;
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scanf("%d", &n);
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for (int i = 0; i < n; i++)
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scanf("%d%d", &a[i].x, &a[i].y);
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std::swap(a[0], *std::min_element(a, a + n, cmp1));
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std::sort(a + 1, a + n, cmp2);
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int top = 0;
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for (int i = 0; i < n; i++)
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{
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while (top >= 2 && cross(a[i] - stk[top - 1], stk[top - 1] - stk[top - 2]) >= 0) top--;
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stk[top++] = a[i];
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}
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stk[top] = stk[0];
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int res = 0;
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if (top == 2)
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res = len2(stk[1] - stk[0]);
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else for (int i = 0, j = 2; i < n; i++)
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{
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while (nxt(j) != i &&
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area(stk[j], stk[i], stk[i + 1]) <=
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area(stk[j + 1], stk[i], stk[i + 1]))
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j = nxt(j);
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res = max(res, max(len2(stk[j] - stk[i]), len2(stk[j] - stk[i + 1])));
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}
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printf("%d", res);
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return 0;
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} |