UVa-10020 minimal coverage **

1 /*
2 * minimum range coverage of Uva-10020-greedy
3 *
4 * very greedy .. For details, see Liu rujia's osai getting started classic.
5 *
6 * test data: http://www.algorithmist.com/index.php/UVa_10020#Input
7 *
8 */
9
10 # include <cstdio>
11 # include <algorithm>
12 using namespace STD;
13
14 const int maxn = 100000 + 5;
15 int casenum, M, intervalnum, anslist [maxn];
16
17 struct sdata {
18 int X, Y;
19 };
20 sdata interval [maxn];
21
22 bool CMP (const sdata LHS, const sdata RHs ){
23 return LHS. x <RHS. X;
24}
25
26 int main (){
27 scanf ("% d", & casenum );
28 while (casenum --){
29 scanf ("% d", & M );
30
31 intervalnum = 0;
32 int tmpx, tmpy;
33 while (scanf ("% d", & tmpx, & tmpy )){
34 if (tmpx = 0 & tmpy = 0)
35 break;
36
37 interval [intervalnum]. x = tmpx;
38 interval [intervalnum ++]. Y = tmpy;
39}
40
41 sort (interval, interval + intervalnum, CMP );
42
43 int cover = 0, cur = 0, nextcover, nextcovernum, I, ANS = 0;
44 bool covered = 0; // pay attention to initialization !! Wa once here
45 while (cur <intervalnum ){
46 nextcover = cover;
47 I = cur;
48 While (I <intervalnum & interval [I]. x <= cover ){
49 If (interval [I]. Y> nextcover ){
50 nextcover = interval [I]. Y;
51 nextcovernum = I;
52}
53 I ++;
54}
55 if (I = cur) break;
56
57 cover = nextcover;
58 anslist [ans ++] = nextcovernum;
59 cur = I;
60 if (cover> = m ){
61 covered = 1;
62 break;
63}
64}
65 if (covered ){
66 printf ("% d \ n", ANS );
67 for (Int J = 0; j <ans; j ++ ){
68 printf ("% d \ n", interval [anslist [J]. X, interval [anslist [J]. y );
69}
70}
71 else printf ("0 \ n ");
72 If (casenum> 0) printf ("\ n ");
73
74}
75
76
77 return 0;
78}

　　　　

1 /*
2. If the range endpoint is an integer, you can store the data in arrays without sorting. The O (n) time can be used.
3: interval [I] = J, indicating that the maximum value of the right endpoint of the range with the left endpoint as I is J ..
4 */
5 # include <cstdio>
6 # include <cstring>
7 using namespace STD;
8
9 const int maxn = 50000 + 10;
10 int M, interval [maxn];
11
12 INT main (){
13 memset (interval,-1, sizeof (interval ));
14
15 scanf ("% d", & M );
16 int tmpa, tmpb;
17 while (scanf ("% d", & tmpa, & tmpb )){
18 if (tmpa = 0 & tmpb = 0) break;
19 if (tmpb <0 | tmpa> = m) continue;
20 if (tmpa <0) tmpa = 0;
21 if (interval [tmpa] <tmpb)
22 interval [tmpa] = tmpb;
23}
24
25 int cover = 0, cur = 0, I = 0, IMAX = 0, num = 0;
26 bool flag = 0;
27 while (I <m ){
28 flag = 0;
29 for (; I <= cover; I ++ ){
30 if (interval [I]> IMAX ){
31 IMAX = interval [I];
32 cur = I;
33}
34}
35 if (IMAX = cover) break;
36
37 cover = IMAX;
38 num ++;
39 if (cover> = m ){
40 flag = 1;
41 break;
42}
43}
44
45 if (FLAG) printf ("% d \ n", num );
46 else printf ("no solution \ n ");
47
48 return 0;
49}