Acwing2024蓝桥杯BFS

AcWing 1355. 母亲的牛奶

bfs: 

#include<iostream>
#include<queue>
using namespace std;
const int N=21;
int A,B,C;
bool flag[N][N][N];
struct node{int a,b,c;
};
queue<node>q;
void check(int a,int b,int c){if(!flag[a][b][c]){q.push({a,b,c});flag[a][b][c]=1;}
}
void bfs(){q.push({0,0,C});flag[0][0][C]=1;while(!q.empty()){auto t=q.front();q.pop();int a=t.a,b=t.b,c=t.c;check(a-min(a,B-b),min(a+b,B),c);check(a-min(a,C-c),b,min(a+c,C));check(min(a+b,A),b-min(b,A-a),c);check(a,b-min(b,C-c),min(c+b,C));check(min(a+c,A),b,c-min(c,A-a));check(a,min(b+c,B),c-min(c,B-b));}return ;
}
int main(){cin>>A>>B>>C;bfs();for(int c=0;c<=C;c++){for(int b=0;b<=B;b++){if(flag[0][b][c]){cout<<c<<" ";break;}}}return 0;
}

dfs:

#include<iostream>
using namespace std;
const int N=21;
int A,B,C;
bool flag[N][N][N];
void dfs(int a,int b,int c){if(flag[a][b][c]) return;flag[a][b][c]=1;dfs(a-min(a,B-b),min(a+b,B),c);dfs(a-min(a,C-c),b,min(a+c,C));dfs(min(a+b,A),b-min(b,A-a),c);dfs(a,b-min(b,C-c),min(c+b,C));dfs(min(a+c,A),b,c-min(c,A-a));dfs(a,min(b+c,B),c-min(c,B-b));return ;
}
int main(){cin>>A>>B>>C;dfs(0,0,C);for(int c=0;c<=C;c++){for(int b=0;b<=B;b++){if(flag[0][b][c]){cout<<c<<" ";break;}}}return 0;
}

AcWing 844. 走迷宫

#include<iostream>
#include<cstring>
#include<queue>
using namespace std;
const int N=110;
int n,m;
typedef pair<int,int>pii;
int mapp[N][N],d[N][N];
int bfs(){memset(d,-1,sizeof d);d[1][1]=0;queue<pii>q;q.push({1,1});int dx[4]={-1,0,1,0},dy[4]={0,1,0,-1};while(q.size()){auto t=q.front();q.pop();for(int i=0;i<4;i++){int x=t.first+dx[i],y=t.second+dy[i];if(x>=1&&x<=n&&y>=1&&y<=m&&d[x][y]==-1&&mapp[x][y]==0){d[x][y]=d[t.first][t.second]+1;q.push({x,y});}}}return d[n][m];
}
int main(){cin>>n>>m;for(int i=1;i<=n;i++) for(int j=1;j<=m;j++) cin>>mapp[i][j];cout<<bfs()<<endl;return 0;
}

AcWing 845. 八数码

STL:unordered_map+bfs:

#include<iostream>
#include<unordered_map>
#include<queue>
using namespace std;
int dx[4]={-1,0,1,0};
int dy[4]={0,1,0,-1};
int bfs(string startt){string last="12345678x";//目标转态queue<string>q;//将字符串和数字联系在一起,字符串表示状态,数字表示距离unordered_map<string,int>d;//初始化q.push({startt});d[startt]=0;while(!q.empty()){auto t=q.front();//记录转态q.pop();int dist=d[t];//记录距离if(t==last) return dist;///终止状态//查找x在字符串中的下标,后转换为在矩阵中的坐标int k=t.find('x');int x=k/3,y=k%3;for(int i=0;i<4;i++){int xx=x+dx[i],yy=y+dy[i];if(xx>=0&&xx<3&&yy>=0&&yy<3){swap(t[k],t[xx*3+yy]);//交换,得到下一种状态if(!d.count(t)){//如果当前状态是第一次遍历,记录距离,入队d[t]=dist+1;q.push({t});}swap(t[k],t[xx*3+yy]);//还原状态}}}return -1;
}
int main(){string s;for(int i=0;i<9;i++){char ch;cin>>ch;s+=ch;}cout<<bfs(s)<<endl;return 0;
}

AcWing 1233. 全球变暖(第九届省赛)

这题在这篇文章里有具体写: 

三.搜索与图论(未完结)-CSDN博客

#include<iostream>
using namespace std;
const int N=1005;
char a[N][N],b[N][N];
int n,res,ans;
int dx[4]={-1,0,1,0};
int dy[4]={0,1,0,-1};
void dfs_all(int x,int y){b[x][y]='.';if(b[x-1][y]=='.'&&x-1>=0&&x-1<n&&y>=0&&y<n){if(b[x][y+1]=='.'&&x>=0&&x<n&&y+1>=0&&y+1<n){if(b[x+1][y]=='.'&&x+1>=0&&x+1<n&&y>=0&&y<n){if(b[x][y-1]=='.'&&x>=0&&x<n&&y-1>=0&&y-1<n){return ;}}}}for(int i=0;i<4;i++){int xx=x+dx[i],yy=y+dy[i];if(b[xx][yy]=='#'){dfs_all(xx,yy);}}
}
void dfs_rest(int x,int y){a[x][y]='.';if(a[x-1][y]=='.'&&x-1>=0&&x-1<n&&y>=0&&y<n){if(a[x][y+1]=='.'&&x>=0&&x<n&&y+1>=0&&y+1<n){if(a[x+1][y]=='.'&&x+1>=0&&x+1<n&&y>=0&&y<n){if(a[x][y-1]=='.'&&x>=0&&x<n&&y-1>=0&&y-1<n){return ;}}}}for(int i=0;i<4;i++){int xx=x+dx[i],yy=y+dy[i];if(a[xx][yy]=='*'||a[xx][yy]=='#'){dfs_rest(xx,yy);}}
}
int main(){cin>>n;for(int i=0;i<n;i++) for(int j=0;j<n;j++) {cin>>a[i][j];b[i][j]=a[i][j];}for(int i=0;i<n;i++) for(int j=0;j<n;j++) if(b[i][j]=='#') {dfs_all(i,j);res++;}for(int i=0;i<n;i++){for(int j=0;j<n;j++){if(a[i][j]=='.'){for(int k=0;k<4;k++){int x=i+dx[k],y=j+dy[k];if(a[x][y]=='#') a[x][y]='*';}}}}for(int i=0;i<n;i++) for(int j=0;j<n;j++) if(a[i][j]=='#') {dfs_rest(i,j);ans++;}cout<<res-ans<<endl;return 0;
}