poj 1113 graham模板（水平序）

這題不多說，裸的模板，graham掃瞄演算法，通過棧比較當前point與棧頂的兩個point是否滿足左轉的關係，不滿足時退棧直到棧空或這滿足時。上**：

/*

memory: 180 kb time: 16 ms
language: c++ result: accepted
by coolwind
*/#include 
#include 
#include 
#include 
using
namespace
std;
#define maxn 2000
const
double pi = acos(-1.0
);struct
point
}point[maxn];
intcmpxy(point a, point b)
intxmul(point a, point b, point o)
double
dis(point a, point b)
point stack[maxn];
inttop;
double graham(int n, int
l) 
int len =top;
stack[++top] = point[n - 1
]; 
for(i = n - 2; i >= 0; i --)
double res = 0
; 
for(i = 0; i < top; i ++)
res += dis(stack[i],stack[i + 1
]); res += l * 2.0 *pi;
return
res;
}int
main()
return0;
}

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