蜗蜗再CityWalk

题目传送门

整体思路：dp

死因：统计答案时没有统计修改次数为0的收益，导致sub1 0，sub3 skipped，痛失70分

代码如下

#include<bits/stdc++.h>
using namespace std;

using ll=long long;
using pii=pair<int,int>;
using pll=pair<ll,ll>;
#define endl '\n';

void gmin(int &x,int y){x=min(x,y);}
void gmax(int &x,int y){x=max(x,y);}
string pt(int st,bool x){return st==1?x?"Yes":"No":x?"YES":"NO";}

int n;
char s[105];
bool dp[101][101][2][201];

void solve(){
    cin>>s+1>>n;
    int l=strlen(s+1);
    memset(dp,0,sizeof dp);
    dp[0][0][0][100]=1;
    for(int i=1;i<=l;i++){
        for(int j=0;j<=n;j++){
            for(int dx=0;dx<=1;dx++){
                for(int p=0;p<=200;p++){
                    if(dp[i-1][j][dx][p]){
                        int tp=p-100;
                        int td=dx==0?-1:1;
                        char ch=s[i];
                        // bu gai
                        if(ch=='W'){
                            // qia jin!
                            int np=tp+td;
                            if(np>=-100&&np<=100){
                                //zai fan wei zhi nei
                                dp[i][j][td==-1?0:1][np+100]=1;
                            }
                        }else{
                            int nd=-td;
                            dp[i][j][nd==-1?0:1][tp+100]=1;
                        }
                        //xiu gai
                        if(j+1>n) continue;
                        char c=ch=='O'?'W':'O';
                        if(c=='W'){
                            int np=tp+td;
                            if(np>=-100&&np<=100){
                                dp[i][j+1][td==-1?0:1][np+100]=1;
                            }
                        }else{
                            int nd=-td;
                            dp[i][j+1][nd==-1?0:1][tp+100]=1;
                        }
                    }
                }
            }
        }
    }
    int ans=0;
    //这里i=0原本写成了i=1
    for(int i=0;i<=n;i++){
        if(i%2!=n%2) continue;
        for(int d=0;d<=1;d++){
            for(int p=0;p<=200;p++){
                if(dp[l][i][d][p]){
                    int tp=p-100;
                    gmax(ans,abs(tp));
                }
            }
        }
    }
    cout<<ans<<endl;
}

int main(){
    cin.tie(0)->sync_with_stdio(0);
    int t=1;
    //cin>>t;
    while(t--) solve();
}