<挑战程序设计竞赛> poj 3320 Jessica's Reading Problem 双指针

地址 http://poj.org/problem?id=3320

解答

使用双指针 在指针范围内是否达到要求

若不足要求则从右进行拓展  若满足要求则从左缩减区域

代码如下  正确性调整了几次 然后被输入卡TLE卡了很久都没意识到......... 

 1 #include <iostream>
 2 #include <map>
 3 #include <set>
 4 #include <algorithm>
 5 #include <assert.h>
 6 #include <stdio.h>
 7 
 8 
 9 using namespace std;
10 
11 int n, m;
12 
13 const int MAX_N = 1000010;
14 
15 int v[MAX_N];
16 
17 set<int> setint;
18 
19 int minLen = 999999;
20 
21 
22 int main()
23 {
24     cin >> n;
25 
26     for (int i = 0; i < n; i++) {
27         //cin >> v[i];
28         scanf("%d",&v[i]);
29         setint.insert(v[i]);
30     }
31 
32     int total = setint.size();
33 
34     int l = 0; int r = 0;
35     map<int, int> mapcover;
36     mapcover[v[l]]++;
37     int count = 1;
38 
39     while(1) {
40         while (count < total) {
41             r++;
42             if (r >= n) {
43                 printf("%d\n", minLen);
44                 return 0;
45             }
46             mapcover[v[r]]++;
47             if (mapcover[v[r]] == 1) {
48                 //说明添加了一个新类型
49                 count++;
50             }
51         }
52 
53         if (count < total) {
54             break;
55         }
56 
57         minLen = min(minLen, r - l + 1);
58         
59         //尝试缩小整个范围 从左端减少
60         mapcover[v[l]]--;
61         if (mapcover[v[l]] == 0) {
62             //说明减少了一个种类
63             count--;
64         }
65         l++;
66     }
67 
68 
69     printf("%d\n", minLen);
70     return 0;
71 }

ac code 1

 1 #include <iostream>
 2 #include <map>
 3 #include <set>
 4 #include <algorithm>
 5 #include <assert.h>
 6 #include <stdio.h>
 7 
 8 
 9 using namespace std;
10 
11 int n, m;
12 
13 const int MAX_N = 1000010;
14 
15 int v[MAX_N];
16 
17 set<int> setint;
18 
19 int minLen = 999999;
20 
21 int main()
22 {
23     cin >> n;
24 
25     for (int i = 0; i < n; i++) {
26         scanf("%d",&v[i]);
27         setint.insert(v[i]);
28     }
29 
30     int total = setint.size();
31 
32     int l = 0; int r = 0;
33     map<int, int> mapcover;
34     mapcover[v[l]]++;
35     int count = 1;
36     while (1) {
37         if (count < total) {
38             r++;
39             if (r >= n) break;
40             mapcover[v[r]]++;
41             //添加了一个新元素 那么元素种类计数+1
42             if (mapcover[v[r]] == 1) count++;
43             
44         }
45         else if(count == total) {
46             minLen = min(minLen, r - l + 1);
47             mapcover[v[l]]--;
48             if (mapcover[v[l]] == 0) {
49                 count--;
50             }
51             l++;
52             if (l >= n) break;
53             if (l > r) {
54                 r = l;
55             }
56         }
57         else {
58             assert(0);
59         }
60 
61     }
62 
63     printf("%d\n",minLen);
64 
65 
66     return 0;
67 }

ac code 2