Poj 2376 greedy range coverage

Poj 2376 greedy range coverage

Question:

Select as few intervals as possible for n intervals to cover 1 ~ T this interval

If output-1 cannot be overwritten

Ideas:

Classic greedy interval coverage

Sort all intervals from small to large to take the interval at the rightmost of the end point.

Code:

 

#include
 
  #include
  
   #include
   
    #include#include
    
     #include
     
      #include
      
       #include
       #include
        
         #include
         
          using namespace std;#define INF 0x3f3f3f3f#define PI acos(-1.0)#define mem(a, b) memset(a, b, sizeof(a))typedef pair
          
            pii;typedef long long LL;//------------------------------const int maxn = 25005;int n, T;struct node{ int s,e; bool operator < (const node nt) const{ return s < nt.s; }}cow[maxn];void init(){ for(int i = 0; i < n; i++){ scanf("%d%d",&cow[i].s,&cow[i].e); } sort(cow, cow + n);}void solve(){ if(cow[0].s > 1){ printf("-1\n"); return; } int start_ = 1, end_ = 1, cnt = 1; for(int i = 0; i < n; i++){ if(cow[i].s <= start_) end_ = max(end_, cow[i].e); else{ cnt++; start_ = end_ + 1; if(cow[i].s <= start_) end_ = max(end_, cow[i].e); else{printf("-1\n"); return; } } if(end_ >= T) break; } if(end_ >= T) printf("%d\n",cnt); else printf("-1\n");}int main(){ scanf("%d%d",&n,&T); init(); solve(); return 0;}
          
         
        
      
     
    
   
  
 

An error occurred when T_T was returned because a condition end> = T... sigh... was rarely judged in the solve function...