Nlogn solution of Toj 4071 longest non-descending sub-sequence

Title Description: Given the coordinates of the n birds in 2D space, the shooter shoots them, the coordinates of the birds required to shoot are getting bigger and larger, i.e. for the first and the i+1 birds, the requirements are fulfilled: xi<=xi+1 && yi <= yi+1. How many birds can be shot at most.

Idea: Sort all points by x-coordinate, with the same x-coordinate, sorted by y-coordinate. The X-direction can meet the limit, the Y-direction of the longest non-descending sub-sequence can be. Due to the large amount of data, it is necessary to take NLOGN optimization algorithm.

1#include <algorithm>2#include <iostream>3#include <cstdio>4 using namespacestd;5 6 Const intN =100000;7 intS[n];8 inttop;9 Ten structNode One { A     intx, y; - } Node[n]; -  the BOOLCMP (Node A, Node B) - { -     if(a.x! = b.x)returnA.x <b.x; -     returnA.y <b.y; + } -  + intMain () A { at     intT; -scanf"%d", &t); -      while(t-- ) -     { -         intN; -scanf"%d", &n); in          for(inti =0; I < n; i++ ) -         { toscanf"%d%d", &node[i].x, &node[i].y); +         } -Sort (node, node +N, CMP); thetop =0; *s[top++] = node[0].y; $          for(inti =1; I < n; i++ )Panax Notoginseng         { -             if(Node[i].y >= S[top-1] ) the             { +s[top++] =node[i].y; A             } the             Else +             { -                 intTMP = Upper_bound (s, S + Top, NODE[I].Y)-s; $S[TMP] =node[i].y;  $             } -         } -printf"%d\n", top);  the     } -     return 0;Wuyi}

The LIS algorithm for NLOGN is not quite understandable and can refer to another article on my blog.

Nlogn solution of Toj 4071 longest non-descending sub-sequence