51nod - 1278 相离的圆 (二分)

 1 #include <iostream>
 2 #include <cstdio>
 3 #include <cmath>
 4 #include <vector>
 5 #include <cstring>
 6 #include <string>
 7 #include <algorithm>
 8 #include <string>
 9 #include <set>
10 #include <functional>
11 #include <numeric>
12 #include <sstream>
13 #include <stack>
14 #include <map>
15 #include <queue>
16 #pragma comment(linker, "/STACK:102400000,102400000")
17 #define CL(arr, val)    memset(arr, val, sizeof(arr))
18 
19 #define ll long long
20 #define inf 0x7f7f7f7f
21 #define lc l,m,rt<<1
22 #define rc m + 1,r,rt<<1|1
23 #define pi acos(-1.0)
24 
25 #define L(x)    (x) << 1
26 #define R(x)    (x) << 1 | 1
27 #define MID(l, r)   (l + r) >> 1
28 #define Min(x, y)   (x) < (y) ? (x) : (y)
29 #define Max(x, y)   (x) < (y) ? (y) : (x)
30 #define E(x)        (1 << (x))
31 #define iabs(x)     (x) < 0 ? -(x) : (x)
32 #define OUT(x)  printf("%I64d\n", x)
33 #define lowbit(x)   (x)&(-x)
34 #define Read()  freopen("a.txt", "r", stdin)
35 #define Write() freopen("b.txt", "w", stdout);
36 #define maxn 1000000000
37 #define N 2510
38 #define mod 1000000000
39 using namespace std;
40 
41 struct node
42 {
43     int x,y;
44     bool operator < (const node a) const
45     {
46         if(x==a.x) return y<a.y;
47         return x<a.x;
48     }
49 }p[50001];
50 int n;
51 int erfen(int a,int b)
52 {
53     int l=a,r=n-1,mid=0;
54     while(l<=r)
55     {
56         mid=(l+r)/2;
57         if(p[mid].x>b) r=mid-1;
58         else l=mid+1;
59     }
60     if(p[mid].x<=b) mid++;
61     if(mid>=n) return n;
62     else return mid;
63 }
64 
65 int main()
66 {
67     //freopen("a.txt","r",stdin);
68     int a,b;
69     scanf("%d",&n);
70     for(int i=0;i<n;i++)
71     {
72         scanf("%d%d",&a,&b);
73         p[i].x=a-b;
74         p[i].y=a+b;
75     }
76     sort(p,p+n);
77     //for(int i=0;i<n;i++)
78     //{
79       //  printf("%d %d\n",p[i].x,p[i].y);
80     //}
81     int num=0;
82     for(int i=0;i<n-1;i++)
83     {
84         int x=erfen(i+1,p[i].y);
85         num+=n-x;
86        // printf("%d %d\n",num,x);
87 
88     }
89     printf("%d\n",num);
90     return 0;
91 }