HDU 5583 Kingdom of Black and White

2015上海区域赛 K题

Description

给一串0和1，然后你可以变一个
这样就分成了若干块
求然后每块长度的平方和最大

Algorithm

两种情况
一种是长度大于1
这样变两边
一种是长度=1，这样3段就练成一段

Hint

貌似必须用vector，不然超时？

Code

#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>
#include <cmath>
#include <vector>
using namespace std;
string s;
void solve()
{
  vector<long long> a;
  cin>>s;
  a.push_back(0);
  a.push_back(1);
  long long ans0 = 0;
  for (int i = 1; i < s.size(); i++)
    if (s[i] == s[i - 1])
      a[a.size() - 1]++;
    else
    {
      a.push_back(1);
    }
  a.push_back(0);
  for (int i = 0; i < a.size(); i++)
    ans0 += (a[i] * a[i]);
  long long ans = ans0;
  for (int i = 1; i < a.size() - 1; i++)
  if (a[i] > 1)
  {
    long long t = ans0 + (a[i] - 1) * (a[i] - 1) + (a[i + 1] + 1) * (a[i + 1] + 1) - a[i] * a[i] - a[i + 1] * a[i + 1];
    if (t > ans) ans = t;
              t = ans0 + (a[i] - 1) * (a[i] - 1) + (a[i - 1] + 1) * (a[i - 1] + 1) - a[i] * a[i] - a[i - 1] * a[i - 1];
    if (t > ans) ans = t;
  }else
    {
      long long t = ans0 + (a[i - 1] + 1 + a[i + 1]) * (a[i - 1] + 1 + a[i + 1]) - (a[i - 1] * a[i - 1] + a[i] * a[i] + a[i + 1] * a[i + 1]);
      if (t > ans) ans = t;
    }
  cout << ans << endl;
}
int main()
{
// freopen("input.txt", "r", stdin);
  int n;
  scanf("%d\n", &n);
  for (int i = 1; i <= n; i++)
  {
    printf("Case #%d: ", i);
    solve();
  }
}