Codeforces Round #547 div3 D

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题目大意

给出两个字符序列，可包含小写字母与'?',相同的字母可以匹配，而可以'?'与任意字符匹配。
求最大的匹配,并将每个匹配的两个字母位置输出

思路

将字符存入对应vector中,优先匹配非'?'的字符.

Code:

#include<bits/stdc++.h> 

#define ll long long 

#define inf 0x3f3f3f3f
using namespace std; 

const int maxn=150010;
char buf1[maxn];
char buf2[maxn];
int n;
vector<int> match[28];
vector<pair<int,int> > ans;
int main(){
	scanf("%d",&n);
	getchar();
	gets(buf1);
	gets(buf2);
	
	for(int i=0;i<n;++i){
		if(buf1[i]=='?'){
			match['z'-'a'+1].push_back(i);
		}else{
			match[buf1[i]-'a'].push_back(i);
		}
	}
	for(int i=0;i<n;++i){
		char ch = buf2[i];
		if(ch=='?'){
			continue;
		}
		if(match[ch-'a'].size()!=0){
			ans.push_back({*(--match[ch-'a'].end())+1,i+1});
			match[ch-'a'].pop_back();
		}else if(match['z'-'a'+1].size()!=0){
			ans.push_back({*(--match['z'-'a'+1].end())+1,i+1});
			match['z'-'a'+1].pop_back();
		}
	}
	
	for(int i=0;i<n;++i){
		char ch = buf2[i];
		if(ch=='?'){
			for(int j=0;j<='z'-'a'+1;++j){
				if(match[j].size()!=0){
					ans.push_back({*(--match[j].end())+1,i+1});
					match[j].pop_back();	
					break;				
				}
			}
		}
	}
	cout << ans.size() << endl;
	for(int i=0;i<ans.size();++i){
		cout << ans[i].first << ' ' << ans[i].second<<endl;
	}
	return 0;
}