D. Monitor Educational Codeforces Round 28

 1 #include <cstdio>
 2 #include <cstdlib>
 3 #include <cmath>
 4 #include <cstring>
 5 #include <time.h>
 6 #include <string>
 7 #include <set>
 8 #include <map>
 9 #include <list>
10 #include <stack>
11 #include <queue>
12 #include <vector>
13 #include <bitset>
14 #include <ext/rope>
15 #include <algorithm>
16 #include <iostream>
17 using namespace std;
18 #define ll long long
19 #define minv 1e-6
20 #define inf 1e9
21 #define pi 3.1415926536
22 #define E  2.7182818284
23 const ll mod=1e9+7;//998244353
24 const int maxn=5e2+10;
25 
26 struct node
27 {
28     int x,y,t;
29 }f[maxn*maxn];
30 
31 int K,s,t,a[maxn][maxn],tot[maxn][maxn]={0};
32 
33 int cmp(node a,node b)
34 {
35     return a.t<b.t;
36 }
37 
38 bool judge()
39 {
40     int i,j;
41     for (i=K;i<=s;i++)
42         for (j=K;j<=t;j++)
43             if (tot[i][j]-tot[i-K][j]-tot[i][j-K]+tot[i-K][j-K]==K*K)
44                 return 1;
45     return 0;
46 }
47 
48 int main()
49 {
50     int q,i,j,l,r,m;
51     scanf("%d%d%d%d",&s,&t,&K,&q);
52     for (i=1;i<=q;i++)
53         scanf("%d%d%d",&f[i].x,&f[i].y,&f[i].t);
54 
55     sort(f+1,f+q+1,cmp);
56 
57     l=1,r=q;
58     while (l<=r)
59     {
60         memset(a,0,sizeof(a));
61         m=(l+r)>>1;
62 
63         for (i=1;i<=m;i++)
64             a[f[i].x][f[i].y]=1;
65         for (i=1;i<=s;i++)
66             for (j=1;j<=t;j++)
67                 tot[i][j]=tot[i-1][j]+tot[i][j-1]-tot[i-1][j-1]+a[i][j];
68         if (judge())
69             r=m-1;
70         else
71             l=m+1;
72     }
73     if (l==q+1)
74         printf("-1");
75     else
76         printf("%d",f[l].t);
77     return 0;
78 }
79 /*
80 2 2 2 4
81 1 2 1
82 1 1 4
83 2 2 3
84 2 1 2
85 
86 2 2 1 4
87 1 2 1
88 1 1 4
89 2 2 3
90 2 1 2
91 
92 2 2 2 0
93 */