最近做的一道交互题

之前做了一道交互题，算是学习一下非传统题的套路吧

http://codeforces.com/contest/727/problem/C

#include <cstdio>using namespace std;int n,a[5050],x[5050],ans;int main(){scanf("%d",&n);for (int i=2;i<=n;i++){printf("? 1 %d\n",i);fflush(stdout);scanf("%d",&x[i-1]);}printf("? 2 3\n");fflush(stdout);scanf("%d",&x[n]);a[2]=(x[1]-x[2]+x[n])/2;a[3]=x[n]-a[2];a[1]=x[1]-a[2];for (int i=4;i<=n;i++) a[i]=x[i-1]-a[1];printf("! ");for (int i=1;i<n;i++) printf("%d ",a[i]);printf("%d\n",a[n]);return 0;}