Find a topic in the search for the Apsara stack management framework-oil deposits

572-oil deposits

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Question link:

Http://uva.onlinejudge.org/index.php? Option = com_onlinejudge & Itemid = 8 & category = 105 & page = show_problem & problem = 513

Question type: Search

Sample input:

1 1*3 5*@*@***@***@*@*1 8@@****@*5 5****@*@@*@*@**@@@@*@@@**@0 0

Sample output:

0122

Analysis:

This question is one of the most basic questions in search. You need to find out how many pieces are connected together. Therefore, enumeration is performed in sequence. When @ is encountered, search is performed. You can perform deep search and extensive search, the purpose is to mark all connected @ as accessed.

The following code uses DFS (Deep Search) and BFS (wide search.

Code 1: DFS

#include<iostream>#include<cstdio>#include<cstring>using namespace std;int m,n;int dir[8][2] = {{-1,0},{-1,1},{0,1},{1,1},                 { 1,0},{1,-1},{0,-1},{-1,-1}};bool vis[105][105];char map[105][105];void dfs(int x, int y){    for(int i=0; i<8; ++i){        int dx=x+dir[i][0], dy=y+dir[i][1];        if(dx>=0 && dx<m && dy>=0 && dy<n && map[dx][dy]=='@' && !vis[dx][dy]){            vis[dx][dy] = true;            dfs(dx, dy);        }    }}int main(){#ifdef LOCAL    freopen("input.txt","r",stdin);#endif    int i,j;    while(scanf("%d %d%*c",&m,&n) && m && n){        for(i=0; i<m; ++i)            gets(map[i]);        memset(vis, 0, sizeof(vis));        int cnt=0;        for(i=0; i<m; ++i){            for(j=0; j<n; ++j){                if(map[i][j]=='@' && !vis[i][j]){                    ++cnt;                    dfs(i, j);                }            }        }        printf("%d\n",cnt);    }           return 0;}

Code 2:

The above is a recursive DFS, but if the data size is large, the recursive method may pose a risk of stack overflow!

The following describes how to simulate the stack instead of writing the DFS recursively.

#include<iostream>#include<cstdio>#include<cstring>#include<stack>using namespace std;int m,n;int dir[8][2] = {{-1,0},{-1,1},{0,1},{1,1},                 { 1,0},{1,-1},{0,-1},{-1,-1}};bool vis[105][105];char map[105][105];struct Node{ int x,y; };stack<Node>st;void dfs(int x, int y){    while(!st.empty()) st.pop();    Node temp;    temp.x = x, temp.y = y;    st.push(temp);    while(!st.empty()){        temp = st.top();        st.pop();        for(int i=0; i<8; ++i){            int dx=temp.x+dir[i][0], dy=temp.y+dir[i][1];            if(dx>=0 && dx<m && dy>=0 && dy<n && map[dx][dy]=='@' && !vis[dx][dy]){                vis[dx][dy] = true;                Node t;                t.x = dx, t.y = dy;                st.push(t);            }        }    }}int main(){#ifdef LOCAL    freopen("input.txt","r",stdin);#endif    int i,j;    while(scanf("%d %d%*c",&m,&n) && m && n){        for(i=0; i<m; ++i)            gets(map[i]);        memset(vis, 0, sizeof(vis));        int cnt=0;        for(i=0; i<m; ++i){            for(j=0; j<n; ++j){                if(map[i][j]=='@' && !vis[i][j]){                    ++cnt;                    dfs(i, j);                }            }        }        printf("%d\n",cnt);    }           return 0;}

Code 3: BFS

#include<iostream>#include<cstdio>#include<cstring>using namespace std;int m,n;int dir[8][2] = {{-1,0},{-1,1},{0,1},{1,1},                 { 1,0},{1,-1},{0,-1},{-1,-1}};bool vis[105][105];char map[105][105];struct Node{ int x,y; };Node que[10000];void bfs(int x,int y){    int front=0, rear=1;    que[0].x = x;    que[0].y = y;    while(front < rear){        Node t=que[front++];        for(int i=0; i<8; ++i){            int dx=t.x+dir[i][0], dy=t.y+dir[i][1];            if(dx>=0 && dx<m && dy>=0 && dy<n && map[dx][dy]=='@' && !vis[dx][dy]){                vis[dx][dy] = true;                Node temp;                temp.x = dx, temp.y = dy;                que[rear++] = temp;            }        }    }}int main(){#ifdef LOCAL    freopen("input.txt","r",stdin);#endif    int i,j;    while(scanf("%d %d%*c",&m,&n) && m && n){        for(i=0; i<m; ++i)            gets(map[i]);        memset(vis, 0, sizeof(vis));        int cnt=0;        for(i=0; i<m; ++i){            for(j=0; j<n; ++j){                if(map[i][j]=='@' && !vis[i][j]){                    ++cnt;                    bfs(i, j);                }            }        }        printf("%d\n",cnt);    }           return 0;}

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