【HDOJ】2428 Stars
先排序后二分。
1 #include <iostream> 2 #include <cstdio> 3 #include <cstring> 4 #include <algorithm> 5 using namespace std; 6 7 #define MAXN 1005 8 9 typedef struct { 10 int x, y; 11 } node_st; 12 13 node_st nodes[MAXN]; 14 int n; 15 16 bool comp(node_st a, node_st b) { 17 if (a.x == b.x) 18 return a.y < b.y; 19 else 20 return a.x < b.x; 21 } 22 23 bool find(int x, int y) { 24 int l=0, r=n-1, mid; 25 26 while (l <= r) { 27 mid = (l+r)>>1; 28 if (nodes[mid].x==x && nodes[mid].y==y) 29 return true; 30 if (nodes[mid].x > x) 31 r = mid - 1; 32 else if (nodes[mid].x < x) 33 l = mid + 1; 34 else if (nodes[mid].y > y) 35 r = mid - 1; 36 else 37 l = mid + 1; 38 } 39 return false; 40 } 41 42 int main() { 43 int t, ans; 44 int i, j; 45 46 scanf("%d", &t); 47 while (t--) { 48 scanf("%d", &n); 49 for (i=0; i<n; ++i) 50 scanf("%d%d", &nodes[i].x, &nodes[i].y); 51 sort(nodes, nodes+n, comp); 52 for (ans=0,i=0; i<n; ++i) { 53 for (j=i+1; j<n; ++j) { 54 if ((nodes[i].x-nodes[j].x)==(nodes[i].y-nodes[j].y) && find(nodes[i].x, nodes[j].y) && find(nodes[j].x, nodes[i].y)) 55 ++ans; 56 } 57 } 58 printf("%d\n", ans); 59 } 60 61 return 0; 62 }
