【codevs2211】WJM2BMR安慰MM记 区间dp

事实上这道题的原型是1258——关路灯，为什么选了这个呢？

废话，因为题目呗= =

言规正传，觉得这道题扯到看不懂的可以去翻codevs1258，说的挺易懂的

其实就是一道区间dp，比较裸的代码，考虑清楚就好

记录过去和回来的最小安慰时间= =

贴代码

var
n,c,i,j,sum:longint;
m,w:array[0..1100] of longint;
a,l,r:array[0..1005,0..1005] of longint;

function min(a,b:longint):longint;
begin
if a<b then exit(a) else exit(b);
end;

begin
readln(n,c);
sum:=0;
for i:=1 to n do
begin
readln(m[i],w[i]);
inc(sum,w[i]);
end;

for i:=1 to n do
begin
a[i,i]:=sum-w[i];
for j:=i+1 to n do a[i,j]:=a[i,j-1]-w[j];
end;

for i:=c+1 to n do
begin
r[c,i]:=r[c,i-1]+(m[i]-m[i-1])*a[c,i-1];
l[c,i]:=r[c,i]+(m[i]-m[c])*a[c,i];
end;

for i:=c-1 downto 1 do
begin
l[i,c]:=l[i+1,c]+(m[i+1]-m[i])*a[i+1,c];
r[i,c]:=l[i,c]+(m[c]-m[i])*a[i,c];
end;

for i:=c-1 downto 1 do
for j:=c+1 to n do
begin
r[i,j]:=min(r[i,j-1]+(m[j]-m[j-1])*a[i,j-1],l[i,j-1]+(m[j]-m[i])*a[i,j-1]);
l[i,j]:=min(l[i+1,j]+(m[i+1]-m[i])*a[i+1,j],r[i+1,j]+(m[j]-m[i])*a[i+1,j]);
end;

writeln(min(l[1,n],r[1,n]));

end.