标签：水平可见直线 hnoi2008 单调栈 ++i com int const cst cpp
传送门：http://www.lydsy.com/JudgeOnline/problem.php?id=1007
按斜率排序，去掉斜率相同时，截距较小的直线（即只保留该斜率下截距最大的直线）。若当前直线与栈顶直线的交点的x坐标<=栈顶直线与栈顶第二条直线的交点的x左边，则pop，直到前者大于后者为止，因为若小于等于，那么栈顶这条直线一定被覆盖。
#include <cstdio>
#include <algorithm>
const int maxn = 50005;
int n, tem_n, top, ori_n;
char book[maxn];
struct line {
long long k, b;
int id;
} a[maxn], stk[maxn];
struct point {
double x, y;
};
bool cmp(const line & aa, const line & ss) {
if (aa.k == ss.k) {
return aa.b > ss.b;
}
return aa.k < ss.k;
}
int main(void) {
scanf("%d", &n);
for (int i = 0; i < n; ++i) {
scanf("%lld%lld", &a[i].k, &a[i].b);
a[i].id = i;
}
std::sort(a, a + n, cmp);
tem_n = 1;
for (int i = 1; i < n; ++i) {
if (a[i].k != a[i - 1].k) {
a[tem_n++] = a[i];
}
}
ori_n = n;
n = tem_n;
for (int i = 0; i < n; ++i) {
while (top > 1 && (stk[top - 1].b - a[i].b) * (stk[top - 1].k - stk[top - 2].k) <= (stk[top - 2].b - stk[top - 1].b) * (a[i].k - stk[top - 1].k)) {
--top;
}
stk[top++] = a[i];
}
for (int i = 0; i < top; ++i) {
book[stk[i].id] = 1;
}
for (int i = 0; i < ori_n; ++i) {
if (book[i]) {
printf("%d ", i + 1);
}
}
return 0;
}
_bzoj1007 [HNOI2008]水平可见直线【单调栈】
标签：水平可见直线 hnoi2008 单调栈 ++i com int const cst cpp
原文地址：http://www.cnblogs.com/ciao-sora/p/6180815.html
