#include<cstdio>
#include<algorithm>
#include<iostream>
#include<cmath>
#include<cstring>

using namespace std;

double dis(double x1,double x2,double y1,double y2){
    double ans=sqrt((x2-x1)*(x2-x1)+(y2-y1)*(y2-y1));
    return ans;
}

int m,n,j,k,x3,y3;
int main(){
    scanf("%d%d%d%d%d%d",&m,&n,&j,&k,&x3,&y3);
    printf("%.2f",dis(m,j,n,k)+dis(j,x3,k,y3)+dis(x3,m,y3,n));
    return 0;
}

上面代码#5是WA，给出的测试点是 23.234 12.123 -99.99 99.99 -1 -100

489.20. 于是我把

int m,n,j,k,x3,y3;

改为了double类型 于是。。。。。。 五个点全都WA掉了5555QAQ