G - Rectangular Polygon
Problem Description
A rectangular polygon is a polygon whose edges are all parallel to the coordinate axes. The polygon must have a single, non-intersecting boundary. No two adjacent sides must be parallel.
Johnny has several sticks of various lengths. He would like to construct a rectangular polygon. He is planning to use sticks as horizontal edges of the polygon, and draw vertical edges with a pen.
Now Johnny wonders, how many sticks he can use. Help him, find the maximal number of sticks that Johnny can use. He will use sticks only as horizontal edges.
Input
Output
. If no polygon can be constructed, output l = 0.
Sample Input
4 1 2 3 5 4 1 2 4 8 4 1 1 1 1
Sample Output
3 0 0 1 0 1 1 3 1 3 2 0 2 0 4 0 0 1 0 1 1 2 1 2 -2 1 -2 1 -1 0 -1
Hint
單組數據
In the first example Johnny uses a stick of length 1 for (0, 0)−(1, 0) edge, a stick of length 2 for (1, 1)−(3, 1) edge and a stick of length 3 for (3, 2) − (0, 2) edge. There is no way to use all four sticks.
題意不是很清楚,就知道是求儘可能多的2堆木杆長度相等,然後搞一搞輸出就行了。
dp[i][j]表示第i根木杆時兩堆差爲j-20000時最多的木杆數,記錄路徑按題目格式轉換輸出就行了。
#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <cstdlib>
#include <vector>
#include <queue>
#include <map>
using namespace std;
const int inf=0x3f3f3f3f;
int dp[105][40005],path[105][40005];
vector<int> vec1,vec2;
int n,a;
int main()
{
scanf("%d",&n);
memset(dp,-inf,sizeof(dp));
int l=20000-n*200;
int r=20000+n*200;
dp[0][20000]=0;
for(int i=1;i<=n;i++){
scanf("%d",&a);
for(int j=l;j<=r;j++){
if(dp[i-1][j]==-inf)continue;
if(dp[i][j+a]<dp[i-1][j]+1){
dp[i][j+a]=dp[i-1][j]+1;
path[i][j+a]=j;
}
if(dp[i][j-a]<dp[i-1][j]+1){
dp[i][j-a]=dp[i-1][j]+1;
path[i][j-a]=j;
}
if(dp[i][j]<dp[i-1][j]){
dp[i][j]=dp[i-1][j];
path[i][j]=j;
}
}
}
printf("%d\n",dp[n][20000]);
int t=20000;
for(int i=n;i>=1;i--){
int tmp=path[i][t];
if(t>tmp) vec1.push_back(t-tmp);
if(t<tmp) vec2.push_back(tmp-t);
t=tmp;
}
int x=0,y=-1;
for(int i=0;i<vec2.size();i++){
printf("%d %d\n",x,++y);
x+=vec2[i];
printf("%d %d\n",x,y);
}
y=0;
for(int i=0;i<vec1.size();i++){
printf("%d %d\n",x,--y);
x-=vec1[i];
printf("%d %d\n",x,y);
}
return 0;
}