结构体数组与结构体排序

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结构体排序使用sort要写cmp来判断 例题 洛谷P5143

#include <iostream>
#include <cstdio>
#include <algorithm>
#include <cmath>
using namespace std;
struct point
{
    int x;
    int y;
    int z;
};
int cmp(point a,point b)
{
    if(a.z<b.z)
    {
        return 1;
    }
    else
    {
        return 0;
    }
}
int main()
{
    int n,i,x1,y1,z1,x2,y2,z2;
    double ans;
    struct point a[50001];
    scanf("%d",&n);
    for(i=0;i<n;i++)
    {
        scanf("%d %d %d",&a[i].x,&a[i].y,&a[i].z);
    }
    sort(a,a+n,cmp);
    ans = 0;
    x1 = a[0].x;
    y1 = a[0].y;
    z1 = a[0].z;
    for(i=1;i<n;i++)
    {
        x2 = a[i].x;
        y2 = a[i].y;
        z2 = a[i].z;
        ans += sqrt(pow(x2-x1,2)+pow(y2-y1,2)+pow(z2-z1,2));
        x1 = x2;
        y1 = y2;
        z1 = z2;
    }
    printf("%.3f",ans);
    return 0;
}