【hoj】2160 bin packing 二分、贪心

#include <iostream>
#include <stdio.h>
#include <cstring>
#include <algorithm>
#define MAX 100000

using namespace std;
int n,length;
int l[MAX];
bool cmp(int a,int b)
{
return a<b;
}
bool judge(int mid)
{
int r = 0,q = 0;
int max = 0;
int tag
;//标记该物是否之前就打包过了
memset(tag,0,sizeof(tag));
for(int i = 0;i < n;i++){
r = length - l[i];
max = i;
for(int j = n-1;j > i;j--){
if((l[j] < r) &&!tag[j]){//尽量找到最能填满剩余空间的物
max = j;
break;
}
}
if(!tag[max]){
q++;
tag[max] = 1;
}
}
if(q < mid)
return false;
else
return true;
}
int main()
{
int high,low,mid,res;
while(cin>>n){
cin>>length;
for(int i = 0;i < n;i++){
cin>>l[i];
}
sort(l,l+n,cmp);
high = n;
low = 0;
res = 0;
while(low <= high){
mid = (low+high)/2;
if(judge(mid)){
res = mid;
low = mid+1;
}
else
high = mid-1;
}
cout<<res<<endl;
}
return 0;
}

#include <iostream>
#include <stdio.h>
#include <string.h>
#include <math.h>
#include <algorithm>
using namespace std;

int li[100003];
int ca[100003];

bool cmp(int a,int b)
{
return a>b;
}
int main()
{
#ifndef ONLINE_JUDGE
freopen("in.txt","r",stdin);
#endif
int n;
int l;

while(scanf("%d",&n)!=EOF)
{
scanf("%d",&l);
for(int i=0;i<n;i++)
{
scanf("%d",&li[i]);
ca[i] = l;
}

sort(li,li+n,cmp);

int ans = 0;
for(int i=0,j=n-1;i<=j;i++)
{
if(li[i] + li[j] <= l)
{
j--;
}
ans++;
}
printf("%d\n",ans);
}
return 0;
}