poj3320 Jessica's Reading Problem

#include <iostream>#include <cstdio>#include <cstring>#include <algorithm>#include <set>#include <map>using namespace std;const int MAX_P = 1e6 + 10; int P;int a[MAX_P];void solve(){// 计算全部知识点的总数 set<int>all; for (int i = 0; i < P; i++) all.insert(a[i]);  int n = all.size();  // 利用尺取法来求解 int s = 0, t = 0, num = 0; map<int, int> count; // 知识点到出现次数的映射 int res = P; for ( ; ; ) { while (t < P && num < n) { if (count[a[t++]]++ == 0) // 出现新的知识点...注意，两个自增符号，无论==是否满足，都会执行  { num++;}}if (num < n) break;res = min(res, t - s);if (--count[a[s++]] == 0) num--; //去掉首页，对应的，首页上的知识点出现次数-1，如果原来就只出现一次，则出现的知识点种类数-1  } cout << res << endl;  }int main(){scanf("%d", &P);for (int i = 0; i < P; i++) scanf("%d", a + i);solve();return 0;}