[问题分解]UVa11054 - Wine trading in Gergovia

#include<bits/stdc++.h>
using namespace std;
struct pp {
    int x1,x2,y1,y2,x,y,num;
}B[5050];
bool cmp1(pp a,pp b) { if(a.x2==b.x2) return a.x1<b.x1; else return a.x2<b.x2; }
bool cmp2(pp a,pp b) { if(a.y2==b.y2) return a.y1<b.y1; else return a.y2<b.y2; }
bool cmp3(pp a,pp b) { return a.num<b.num; }
int main()
{
    int n;
    while(scanf("%d",&n)&&n){
        for(int i=0;i<n;i++) { scanf("%d%d%d%d",&B[i].x1,&B[i].y1,&B[i].x2,&B[i].y2); B[i].x=0; B[i].y=0; B[i].num=i+1; }
        sort(B,B+n,cmp1);
        int AA=0,BB=0;
        for(int i=1;i<=n;i++)
        for(int j=0;j<n;j++) {
            if(B[j].x1<=i &&B[j].x2>=i &&!B[j].x)
            {
                B[j].x=i;  AA++; break;
            }
        }
        sort(B,B+n,cmp2);

        for(int i=1;i<=n;i++)
        for(int j=0;j<n;j++) {
            if(B[j].y1<=i &&B[j].y2>=i &&!B[j].y)
            {
                B[j].y=i;  BB++; break;
            }
        }
        if(AA==n&&BB==n){
            sort(B,B+n,cmp3); for(int i=0;i<n;i++) printf("%d %d\n",B[i].x,B[i].y);
        } else printf("IMPOSSIBLE\n");
    }
    return 0;
}