算法专题 最大连续子段和 普及组【2014】四2 Pascal版

const
    SIZE = 100;
var
    matrix: array [1..SIZE, 1..SIZE] of integer;
    rowsum: array [1..SIZE, 0..SIZE] of integer;
    // rowsum[i, j]记录前 i 行前 j 个数的和
    m, n, i, j, first, last, area, ans: integer;
begin
    read(m, n); 
    for i := 1 to m do
        for j := 1 to n do
            read(matrix[i, j]);
    ans := matrix[1,1];//
    for i := 1 to m do
    rowsum[i,0]:=0 ;
    for i := 1 to m do
        for j := 1 to n do
            rowsum[i, j] := rowsum[i,j-1]+matrix[i,j]  ;
    for first := 1 to n do
        for last := first to n do
        begin
            area:=0 ;
            for i := 1 to m do
            begin
                area := area + rowsum[i,last]-rowsum[i,first-1] ;
                if (area > ans) then
                    ans := area;
                if (area < 0) then
                    area := 0;
            end;
        end;
    writeln(ans);
end.