Update 2954.Count-the-Number-of-Infection-Sequences.cpp

Author: wisdompeak

Math/2954.Count-the-Number-of-Infection-Sequences/2954.Count-the-Number-of-Infection-Sequences.cpp

@@ -2,56 +2,39 @@ using LL = long long;
 class Solution {
  LL power[100005];
  LL fact[100005];
- LL M = 1e9+7;
  LL mod = 1e9+7;
 public:
  int numberOfSequence(int n, vector<int>& sick) 
  {
  power[0] = 1;
  for (int i=1; i<=n; i++)
- power[i] = power[i-1]*2 % M;
+ power[i] = power[i-1]*2 % mod;
 
  fact[0] = 1;
  for (int i=1; i<=n; i++)
- fact[i] = fact[i-1]*i % M;
+ fact[i] = fact[i-1]*i % mod;
 
  vector<int>groups;
  for (int i=0; i<sick.size(); i++)
  {
  if (i==0)
- {
- if (sick[0]!=0)
- groups.push_back(sick[i]);
- } 
+ groups.push_back(sick[i]);
  else 
- {
- if (sick[i]-sick[i-1]-1>0)
- groups.push_back(sick[i]-sick[i-1]-1); 
- }
- 
+ groups.push_back(sick[i]-sick[i-1]-1); 
  }
- if (sick.back()!=n-1)
- groups.push_back(n-1-sick.back());
- 
- // for (int x: groups) cout<<x<<" "; cout<<endl;
+ groups.push_back(n-1-sick.back());
 
  int total = accumulate(groups.begin(), groups.end(), 0);
 
  LL ret = fact[total];
- for (int x: groups)
- {
- // cout<<fact[x]<<endl;
- ret = ret * inv(fact[x]) % M;
- }
- 
- // cout<<ret<<endl;
- 
- 
+ for (int x: groups) 
+ ret = ret * inv(fact[x]) % mod;
+ 
  for (int i=1; i<sick.size(); i++)
  {
  int x = sick[i]-sick[i-1]-1;
  if (x>0)
- ret = ret * power[x-1] % M;
+ ret = ret * power[x-1] % mod;
  }
 
  return ret;