相关链接
题目传送门：http://www.lydsy.com/JudgeOnline/problem.php?id=4236
神犇题解：http://www.cnblogs.com/qscqesze/p/4775481.html
解题报告
如果字符集大小只有2的话，那一个搞成1另一个搞成-1就好啦！
但这题字符集大小为3，于是我们从数组拓展到三维坐标系就好啦！
然后搞一个map什么的装一装，时间复杂度:$O(nlogn)$
Code
#include<bits/stdc++.h>
#define LL long long
using namespace std;
int n,vout;
map<pair<int,int>, int> m;
inline int read() {
char c=getchar();
while (c!='J'&&c!='O'&&c!='I') c=getchar();
if (c == 'J') return 1;
else if (c == 'O') return 2;
else return 3;
}
int main() {
cin>>n;
pair<int,int> cur(0,0);
for (int i=1,w;i<=n;i++) {
w = read();
if (w == 1) cur.first++;
else if (w == 2) cur.second++;
else cur.first--, cur.second--;
if (m[cur]) vout = max(vout, i - m[cur]);
else m[cur] = i;
if (!cur.first && !cur.second) vout = max(vout, i);
}
cout<<vout<<endl;
return 0;
}
You have brought up a very fantastic points, thanks for the post.
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