codeforce 621B Wet Shark and Bishops

对角线 x1+y1=x2+y2 或者x1-y1=x2-y2

 1 #include<iostream>
 2 #include<string>
 3 #include<algorithm>
 4 #include<cstdlib>
 5 #include<cstdio>
 6 #include<set>
 7 #include<map>
 8 #include<vector>
 9 #include<cstring>
10 #include<stack>
11 #include<cmath>
12 #include<queue>
13 #include <bits/stdc++.h>
14 using namespace std;
15 #define INF 0x3f3f3f3f
16 #define ll long long
17 #define clc(a,b) memset(a,b,sizeof(a))
18 const int maxn=4010;
19
20 int main()
21 {
22     int n;
23     int x,y;
24     int a[maxn];
25     int b[maxn];
26     scanf("%d",&n);
27     clc(a,0);
28     clc(b,0);
29     for(int i=0;i<n;i++)
30     {
31         scanf("%d%d",&x,&y);
32         a[x+y]++;
33         b[x-y+2000]++;
34     }
35     ll sum=0;
36     for(int i=0;i<=2000;i++)
37     {
38         if(a[i]%2)
39             sum+=(a[i]-1)/2*a[i];
40         else
41             sum+=a[i]/2*(a[i]-1);
42     }
43     for(int i=-999+2000;i<=999+2000;i++)
44     {
45         if(b[i]%2)
46             sum+=(b[i]-1)/2*b[i];
47         else
48             sum+=b[i]/2*(b[i]-1);
49     }
50     printf("%I64d\n",sum);
51     return 0;
52 }