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题目：输入n个整数,找到其中最小的K个数。例如输入4,5,1,6,2,7,3,8这8个数字，则最小的4个数字是1,2,3,4.
1 #include<iostream> 2 using namespace std; 3 int partition(int *input,int n,int s,int t) 4 { 5 if(input==NULL||n<=0||s<0||t>n-1) 6 return 0; 7 int tmp; 8 if(s<t) 9 { 10 tmp=input[s]; 11 while(s<t) 12 { 13 while(s<t&&input[t]>=tmp) 14 t--; 15 input[s]=input[t]; 16 while(s<t&&input[s]<=tmp) 17 s++; 18 input[t]=input[s]; 19 } 20 input[s]=tmp; 21 } 22 return s; 23 } 24 25 26 void getleastnumbers(int *input,int n,int *output,int k) 27 { 28 if(input==NULL||output==NULL||k>n||n<=0||k<=0) 29 return; 30 int start=0; 31 int end=n-1; 32 int index; 33 index=partition(input,n,start,end); 34 while(index!=k-1) 35 { 36 if(index>k-1) 37 { 38 end=index-1; 39 index=partition(input,n,start,end); 40 } 41 else 42 { 43 start=index+1; 44 index=partition(input,n,start,end); 45 } 46 } 47 for(int i=0;i<k;i++) 48 output[i]=input[i]; 49 } 50 int main() 51 { 52 int input[]={4,5,1,6,2,7,3,8,3}; 53 int output[9]; 54 int k; 55 cin>>k; 56 getleastnumbers(input,9,output,k); 57 for(int i=0;i<k;i++) 58 cout<<output[i]<<" "; 59 cout<<endl; 60 return 1; 61 }
1 #include<iostream> 2 #include<set> 3 using namespace std; 4 typedef multiset<int,greater<int> > intset; 5 typedef multiset<int,greater<int> >::iterator setIterator; 6 7 void getleastnumbers(int *input,int n,intset &leastnumbers,int k) 8 { 9 leastnumbers.clear(); 10 if(k<1||n<k) 11 return; 12 for(int i=0;i<n;i++) 13 { 14 if(leastnumbers.size()<k) 15 leastnumbers.insert(input[i]); 16 else 17 { 18 19 setIterator iterGreatest=leastnumbers.begin(); 20 if(input[i]<*iterGreatest) 21 { 22 leastnumbers.erase(iterGreatest); 23 leastnumbers.insert(input[i]); 24 } 25 } 26 } 27 } 28 29 int main() 30 { 31 int input[]={4,5,1,6,2,7,3,8,3}; 32 int k; 33 intset myset; 34 cin>>k; 35 getleastnumbers(input,9,myset,k); 36 for(setIterator it=myset.begin();it!=myset.end();++it) 37 cout<<*it<<" "; 38 cout<<endl; 39 return 1; 40 }
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原文地址：http://www.cnblogs.com/wxdjss/p/5487197.html
