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// pre[i][j] - sum of all values which are above it or left of it
vector<vector<int>> pre;
 
void pre2d(vector<vector<int>> &arr)
{
    int r = arr.size(), c = arr[0].size();
    pre.resize(r, vi(c));
    pre[0][0] = arr[0][0];
 
    // Base cases
    for (int i = 1; i < c; i++)
        pre[0][i] = pre[0][i - 1] + arr[0][i];
 
    for (int i = 1; i < r; i++)
        pre[i][0] = pre[i - 1][0] + arr[i][0];
 
    for (int i = 1; i < r; i++)
    {
        for (int j = 1; j < c; j++)
            pre[i][j] = pre[i - 1][j] + pre[i][j - 1] - pre[i - 1][j - 1] + arr[i][j];
    }
}
 
// returns value of submatrix with start coordinates as {sx, sy}
int val(int sx, int sy, int ex, int ey)
{
    if (!sy && !sx)
        return pre[ex][ey];
 
    if (!sy)
        return pre[ex][ey] - pre[sx - 1][ey];
 
    if (!sx)
        return pre[ex][ey] - pre[ex][sy - 1];
 
    return pre[ex][ey] - pre[ex][sy - 1] - (pre[sx - 1][ey] - pre[sx - 1][sy - 1]);
}

prog.cpp:2:1: error: ‘vector’ does not name a type
 vector<vector<int>> pre;
 ^~~~~~
prog.cpp:4:12: error: variable or field ‘pre2d’ declared void
 void pre2d(vector<vector<int>> &arr)
            ^~~~~~
prog.cpp:4:12: error: ‘vector’ was not declared in this scope
prog.cpp:4:19: error: ‘vector’ was not declared in this scope
 void pre2d(vector<vector<int>> &arr)
                   ^~~~~~
prog.cpp:4:26: error: expected primary-expression before ‘int’
 void pre2d(vector<vector<int>> &arr)
                          ^~~
prog.cpp: In function ‘int val(int, int, int, int)’:
prog.cpp:28:16: error: ‘pre’ was not declared in this scope
         return pre[ex][ey];
                ^~~
prog.cpp:31:16: error: ‘pre’ was not declared in this scope
         return pre[ex][ey] - pre[sx - 1][ey];
                ^~~
prog.cpp:34:16: error: ‘pre’ was not declared in this scope
         return pre[ex][ey] - pre[ex][sy - 1];
                ^~~
prog.cpp:36:12: error: ‘pre’ was not declared in this scope
     return pre[ex][ey] - pre[ex][sy - 1] - (pre[sx - 1][ey] - pre[sx - 1][sy - 1]);
            ^~~

Standard output is empty