TJU 2199. A+B Problem May 30, 2010

TJU 2199. A+B Problem
AC
This problem requires Sorting and Searching(Binary) approch

#include<stdio.h>
#include<string.h>
#include<stdlib.h>
#include<math.h>
#include<iostream>
#include<algorithm>
using namespace std;


int main()
{
 int i,j,k;
 int a[1009],n;
 int tmp,diff;
 int low,mid,high,flag,num;
 while(1){
    scanf("%d",&n);
    if(n==0) break;
    for(i=0;i<n;i++)
       scanf("%d",&a[i]);
    
    sort(a,a+n);//sort
    
    for(i=n-1;i>=0;i--){
       tmp=a[i];
       for(j=i-1;j>=0;j--){
         diff=tmp-a[j];
         high=j-1;low=0;
         flag=0;
         mid=(low+high)/2;
         while(low<=high){//binary search
            mid=(low+high)/2;
            
            if(a[mid]==diff){ flag=1;num=tmp;goto down;}
            else if(diff<a[mid]){high=mid-1;}
            else if(diff>a[mid]){low=mid+1;}
         }
       }
      
    }
     down:
          if(flag==1) printf("%d\n",tmp);
          else printf("-1\n");
   }    

return 0;
}

How to use binary_search() November 28, 2009

How to use binary_search()

#include <algorithm>
#include <iostream>
#include <utility>
using namespace std;
#define N 20
int a[N];
int main(){
    sort(a,a+N);
    if(binary_search(a,a+N,1)){
        cout<<"OK";
    }
}