I solved this problem https://codeforces.net/problemset/problem/1335/F get memory limit exceed on test case 46 by this solution https://codeforces.net/contest/1335/submission/76658211 and get accepted by this solution https://codeforces.net/contest/1335/submission/77233784. I only change the type to resize and initialize the vector;

// where n*m <= 1e6;

vector<vector<int> > vis;
   vector<vector<int> > cur;
   vector<vector<int> > dis;
   vector<vector<int> > size;
   vector<vector<int> > r;
   vector<vector<char> > c;
   vector<vector<char> > path;

vis.resize(n);
path.resize(n);
cur.resize(n); // by this get memory limit exceed.
c.resize(n);
dis.resize(n);
r.resize(n);
siz.resize(n);
for(int i = 0; i < n; i++){
    vis[i].resize(m, 0);
    path[i].resize(m);
    cur[i].resize(m, 0);
    c[i].resize(m);
    dis[i].resize(m, -1);
    r[i].resize(m, -1);
    siz[i].resize(m, 0);
    for(int j = 0; j < m; j++){
        siz[i][j] = vis[i][j] = cur[i][j] = 0;
        r[i][j] = dis[i][j] = -1;
        cin >> c[i][j];
    }
}


vis.resize(n);
path.resize(n);
cur.resize(n);
c.resize(n);
dis.resize(n);
r.resize(n);  //  by this get accepted
siz.resize(n);
for(int i = 0; i < n; i++){
    vis[i].resize(m);
    cur[i].resize(m);
    dis[i].resize(m);
    r[i].resize(m);
    siz[i].resize(m);
    c[i].resize(m);
    path[i].resize(m);
    for(int j = 0; j < m; j++){
        siz[i][j] = vis[i][j] = cur[i][j] = 0;
        r[i][j] = dis[i][j] = -1;
        cin >> c[i][j];
    }
}