一些失误总结

总结

世间起因于洪水灌溉算法竟然我没写对，在检查了好几遍之后发现竟然是二维数组的初始化为1出现了问题，memset不可以用！！于是写下总结

代码

 #include<iostream>
 #include<algorithm>
#include<cstring>
#include<queue>

using namespace std;
int n,m;
typedef pair<int,int> PII;
int a[1000][1000] = {1};
 PII start,endd;
int dx[]={0,0,1,-1};
int dy[]={1,-1,0,0};
void sov(){
    queue<PII>q;
    q.push(start);
    int ans = 1;
    while(q.size()){
        PII tp = q.front();
        q.pop();
        int x= tp.first;
        int y = tp.second;
        a[x][y] = 1;
        for(int i =0 ; i < 4; i++){
            int xx = x + dx[i];
            int yy = y + dy[i];
            if(xx < 0 || yy < 0 || xx > n || yy > m ||a[xx][yy] == 1) continue;
            else{
                q.push({xx,yy});
                a[xx][yy] = 1;
                ans++;
            }
        }
    }
    
    q.push(endd);
    int ans2 = 1;
    while(q.size()){
        PII tp = q.front();
        q.pop();
        int x= tp.first;
        int y = tp.second;
        a[x][y] = 1;
        for(int i =0 ; i < 4; i++){
            int xx = x + dx[i];
            int yy = y + dy[i];
             if(xx < 0 || yy < 0 || xx > n || yy > m ||a[xx][yy] == 1) continue;
            else{
                q.push({xx,yy});
                a[xx][yy] = 1;
                ans2++;
            }
        }
    }
    if(ans < ans2) cout << ans2 <<endl;
    else cout << ans << endl;   
}


int main(){
   
    int flag = 0;
    cin >> n >> m;
    
    for(int i = 0; i <= n; i++){
    	for(int j = 0; j <= m; j++)
    	 a[i][j] = 1;
	}
    
    for(int i =1; i <= n; i++)
        for(int j = 1; j <=m; j++ )
        {
            cin >> a[i][j];
            if(!flag && a[i][j] == 0)
            {
                start.first = i;
                start.second = j;
                flag = 1;
            }
            else if (a[i][j] == 0){
                endd.first = i;
                endd.second = j;
            }
        }
     sov();
            
}
//不能通过memset 将数组赋值除了0 或者-1 以外的任何值 
//不能将a[100][100] = {1}将该数组全部赋值为1
//可以通过vector<vector<int>> a(n, vector<int>(m, 1));