纪念品分组 pascal

vara:array[1..100000] of longint /卜猛/记型谨桥录纪念晌铅品的价格

i,j,w,n,x:longint //w为每组价格上限，x为分组数，n为总件数procedure qsort(l,r:longint)

var i,j,m,p:longint

begin

i:=lj:=rm:=a[(l+r) div 2]

repeat

while a[i]<m do inc(i)

while a[j]>m do dec(j)

if i<=j then

begin p:=a[i]a[i]:=a[j]a[j]:=pinc(i)dec(j)end

until i>j

if i<r then qsort(i,r)

if l<j then qsort(l,j)

endbegin

assign(input,'group.in') rewrite(input)

assign(output,'group.out') rewrite(output)

readln(w)readln(n)

for i:=1 to n do readln(a[i])

qsort(1,n) //用一次快排把纪念品按价格排列，从低到高

i:=1j:=nx:=0 //i指向价格最低的纪念品，j指向最高的

repeat

if i=j then begin inc(x)breakend//如果只剩下一件纪念品，单独为一组

if a[j]+a[i]<=w then begin inc(i)dec(j)inc(x)end //如果两件纪念品之和不超过w就为一组

else begin dec(j)inc(x)end //如果超过w就让j指向的纪念品单独为一组，i不改变

until i>j //直至分完

writeln(x)

close(input) close(output)

end.

var

w,n,i,j,ans:longint

a:array[0..30001] of longint

procedure qsort(r,l:longint)

var

i,j,k:longint

begin

i:=r

j:=l

k:=a[(i+j) shr 1]

repeat

while a[i]<k do inc(i)

while a[j]>k do dec(j)

if i<=j then begin

a[0]:=a[i]

a[i]:=a[j]

a[j]:=a[0]

inc(i)

dec(j)

end

until i>j

if i<l then qsort(i,l)

if r<j then qsort(r,j)

end

begin

readln(w)

readln(n)

for i:=1 to n do readln(a[i])

qsort(1,n)

i:=1j:=n

while i<=j do begin

if i=j then begin

if a[i]<=w then inc(ans)

break

end

if a[i]+a[j]<=w then begin

inc(ans)

inc(i)

dec(j)

end else if a[j]<=w then begin

inc(ans)

dec(j)

end else dec(j)

end

writeln(ans)

end.

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