50147. Circles

#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>

#define max(a,b) ((a)>(b)?(a):(b))

int n;
uint64_t arr[1000105];

int cmp(const void* a, const void* b){
    return *(uint64_t*)a - *(uint64_t*)b;
}

int main(){
    scanf("%d", &n);
    for(int i = 0; i < n; i++){
        uint64_t x, y; scanf("%llu %llu", &x, &y);
        arr[i] = x * x + y * y;
    }
    qsort(arr, n, sizeof(uint64_t), cmp);

    int cnt = 1;
    int max_cnt = 1;
    int max_rad = arr[0];
    // for(int i = 0; i < n; i++) printf("%llu ", arr[i]);
    for(int i = 1; i < n; i++){
        if(arr[i - 1] == arr[i]) cnt++;
        else cnt = 1;
        if(cnt > max_cnt) max_cnt = cnt, max_rad = arr[i];
        else if(cnt == max_cnt) max_rad = arr[i];
    }
    printf("%d\n", max_rad);
}