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我必须要说的是输出时printf("%f", a);而不是%lf那样会wa这是我付出了n个小时得到的教训

#include<iostream>
#include<stdio.h>
#include<string.h>
#include<cmath>
#include<algorithm>
using namespace std;
const int maxa = 1005;
struct edge{
    int x, y;
}e[maxa], q[maxa];
int cmp(edge a, edge b){
    if(a.x != b.x)
        return a.x < b.x;
    return a.y < b.y;
}
int det(int x1, int y1, int x2, int y2){
    return x1*y2 - x2*y1;
}
int cross(edge a, edge b, edge c, edge d){
    return det(b.x - a.x, b.y -a.y, d.x - c.x, d.y - c.y);
}
int make_tubao(int n){
    sort(e, e+n, cmp);
    int m = 0;
    for(int i = 0; i < n; i++){
        while(m >= 2 && cross(q[m-2], q[m-1], q[m-1], e[i])>= 0){
            m--;
        }
        q[m++] = e[i];
    }
    int k = m;
    for(int i = n-2; i >= 0; i--){
        while(m > k && cross(q[m-2], q[m-1], q[m-1], e[i])>= 0){
            m--;
        }
        q[m++] = e[i];
    }
    return m;
}
double dis(edge a, edge b){
    return sqrt((b.x - a.x)*(b.x - a.x) + (b.y-a.y)*(b.y-a.y));
}
int print(int n, int m){
    n = make_tubao(n);
    double ans = 0;
    for(int i = 0;i < n-1; i++){
       // printf("%d %d ", q[i].x, q[i].y);
        ans += dis(q[i], q[i+1]);
    }
    printf("%.0f ", ans + 3.1415926*2*m);
}
int main(){
    int n, m;
    while(scanf("%d%d", &n, &m)!=EOF){
        for(int i = 0 ; i < n; i++){
            scanf("%d%d", &e[i].x, &e[i].y);
        }
        print(n, m);
    }
}