UVA 11572 Unique Snowflakes .

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题目地址：http://vjudge.net/problem/UVA-11572

第一种用set做

#include <bits/stdc++.h>using namespace std;#define REP(i,a,b)  for(int i=a;i<=(int)(b);++i)#define REPD(i,a,b) for(int i=a;i>=(int)(b);--i)int A[(int)1e6+5];int main(int argc, char const *argv[]){int T,n; scanf("%d",&T);while(T--&&scanf("%d",&n)==1){REP(i,1,n) scanf("%d",&A[i]);set<int> st;int L=1,R=1,ans=1;while(R<=n){while(R<=n&&!st.count(A[R])) st.insert(A[R]),R++;ans=max(ans,R-L);st.erase(A[L]); L++;}printf("%d\n", ans);}return 0;}

第二种，用last保存上一个相同数字的坐标来代替set查找

#include <bits/stdc++.h>using namespace std;#define REP(i,a,b)  for(int i=a;i<=(int)(b);++i)#define REPD(i,a,b) for(int i=a;i>=(int)(b);--i)int A[1000000+5],last[1000000+5];int main(int argc, char const *argv[]){int T,n; scanf("%d",&T);while(T--&&scanf("%d",&n)==1){map<int,int> cur;REP(i,1,n) {scanf("%d",&A[i]);if(cur.count(A[i])==0) last[i]=-1;else last[i]=cur[A[i]];cur[A[i]]=i;}int L=1,R=1,ans=1;while(R<=n){while(R<=n&&last[R]<L) R++;ans=max(ans,R-L);L++;}printf("%d\n", ans);}return 0;}

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