Pipe Fitter and the Fierce Dogs

Pipe Fitter and the Fierce Dogs

[I Asia 2016]

After understanding the problem, that is a very silly DP

Then difficulty in understanding the problem, understand the illegal status

#include <bits/stdc++.h>
 
using namespace std;
const int maxn = 1e4+2;
int dp[maxn][3];
bool mp[maxn][maxn];
int main(){
    int w,h,k,n;
    scanf("%d%d%d%d",&w,&h,&k,&n);
    for(int i=1,u,v;i<=n;++i){
        scanf("%d%d",&u,&v);
        mp[v][u]=1;
    }
    int sp=(w+1)>>1;
    if(!(w&1)) --w;
    if(k<sp){
        puts("-1");
        return 0;
    }
    k-=sp;
    int all=sp*((h+1)/2-1);
    int ans=0;
    for(int i=3;i<=h;i+=2){
        dp[1][0]=0x3f3f3f3f;
        dp[1][1]=1+mp[i-1][1];
        dp[1][2]=1+mp[i-1][2];
        for(int j=3;j<=w;j+=2){
            dp[j][0]=dp[j-2][2]+mp[i-1][j-1]+1;
            dp[j][1]=min(dp[j-2][0],dp[j-2][1])+mp[i-1][j]+1;
            dp[j][2]=min(dp[j-2][0],dp[j-2][1])+mp[i-1][j+1]+1;
        };
        ans+=min(dp[w][0],dp[w][1])-sp;
    }
    if(ans>=k){
        ans-=k;
        all-=k;
        all+=ans;
        printf("%d\n",all);
    }else{
        all-=k;
        printf("%d\n",max(0,all));
    }
    return 0;
}