Educational Codeforces Round 24 D. Multicolored Cars（思维）

题目链接

#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
const int maxn=1e6+1;
vector<int>pos[maxn],temp;
int n,A,a[maxn],cnt[maxn],num[maxn],ans[maxn],sum;
int main()
{
	scanf("%d%d",&n,&A);
	for(int i=1;i<=n;++i)
	{
		cnt[i]=cnt[i-1];
		scanf("%d",&a[i]);
		if(a[i]==A) cnt[i]++,sum++,temp.push_back(i);
		pos[a[i]].push_back(i);
	}
	for(int i=1;i<maxn;++i)
	{
		int size=pos[i].size();
		if(i==A||size==0||size<sum) continue;
		for(int j:temp)
		{
			int now=pos[i][num[i]++];
			//cout<<i<<" "<<now<<endl;
			if(now<j) ans[i]++;
		}
		if(ans[i]==sum) {
			printf("%d\n",i);return 0;
		}
	}
	printf("-1\n");
}