从小到大排序,然后依次往后二分搜索
#include<bits/stdc++.h> #include<iostream> #include<algorithm> using namespace std; typedef long long ll; const ll maxn=5e5+50; ll aim,n,cnt,num[maxn]; struct node{ ll a,b; }N[maxn]; int main() { scanf("%lld%lld",&aim,&n); for(ll i=1;i<=n;i++) scanf("%lld",&num[i]); sort(num+1,num+n+1); for(ll i=1;i<=n;i++) { ll l=i,r=n,mid; while(r>=l) { mid=(l+r)/2; if(num[mid]+num[i]>=aim) r=mid-1; else if(num[mid]+num[i]<aim) l=mid+1; //printf("l:%lld r:%lld mid:%lld %lld %lld %lld %lld\n",l,r,mid,num[i],num[l],num[mid],num[r]); } if(num[i]+num[l]==aim && l!=i) { N[++cnt].a=num[i]; N[cnt].b=num[l]; } //printf("sdjhiusuishf\n"); } if(cnt==0) { printf("No Solution\n"); return 0; } for(int i=1;i<=cnt;i++) { printf("%lld %lld\n",N[i].a,N[i].b); } return 0; }