Codeforces Round #811 (Div. 3)D. Color with Occurrences

题目大意：给出一个文章t和n个字符串s1,s2...sn；

　　问能否用这n个字符串将整个文章覆盖；

思路：贪心（最小区间覆盖)

　　记录每个字符串能够覆盖的所有位置（起点，终点，编号)

　　排序后贪心的求出是否能够将所有点覆盖

 1 # include<iostream>
 2 # include<bits/stdc++.h>
 3 using namespace std;
 4 # define int long long
 5 # define endl "\n"
 6 const int N = 2e5 + 10, INF = 0x3f3f3f3f3f;
 7 struct node {
 8     int l, r, id;//起点，终点，编号
 9 };
10 string s;
11 bool cmp(node a, node b) {
12     if (a.l != b.l) return a.l < b.l;
13     return a.r < b.r;
14 }
15 vector<node> se;
16 int length;
17
18 bool check(int start, string t) {
19     int maxv = length - start + 1;
20     if (maxv < t.size()) return false;
21     for (int i = start, j = 0; i <= start + t.size() - 1; ++i, ++j) {
22         if (t[j] != s[i]) return false;
23     }
24     return true;
25 }
26
27 void solve() {
28
29     int n;
30     cin >> s >> n;
31     se.clear();
32     length = s.size();
33     s = "?" + s;
34     for (int i = 1; i <= n; ++i) {
35         string t;
36         cin >> t;
37         int len = t.size();
38         for (int j = 1; j  <= length; ++j) {
39             if (check(j, t)) se.push_back({j, j + len - 1, i});//记录每个字符串能够覆盖的点
40         }
41     }
42     sort(se.begin(), se.end(), cmp);//以起始点为基准从小到大排序
43     bool ok = false;
44     int start = 1, ed = length;
45     vector<pair<int, int>> ans;
46     for (int i = 0; i < se.size(); ++i) {
47         int j = i, r = -INF;
48
49         int t = 0;
50         while (j < se.size() && se[j].l <= start) {
51             if (se[j].r > r)  //寻找能够覆盖区间最长的字符串
　　　　　　　　　{
52                 r = se[j].r;
53                 t = j;
54             }
55             j++;
56         }
57         if (r < start) break;
58         start = r+1,i = j-1;
59         ans.push_back({se[t].id,se[t].l});
60         if(r>= ed){
61             ok = true;
62             break;
63         }
64     }
65     if(ok){
66         cout<<ans.size()<<endl;
67         for(auto it:ans)cout<<it.first<<" "<<it.second<<endl;
68     }
69     else cout<<-1<<endl;
70 }
71 int tt;
72 signed main() {
73     ios::sync_with_stdio(false);
74     cin.tie(0);
75     cout.tie(0);
76     cin >> tt;
77     while (tt--)solve();
78
79
80     return 0;
81 }