1125 咸鱼商店(二分+01背包) “玲珑杯”线上赛

题目
题意：求出满足在背包容量内，背包价值大于k的所有情况中，找到最小价值是最大的那一种情况。

#include <iostream>#include <cstdio>#include <cstdlib>#include <algorithm>#include <cstring>#include <string>#include <cmath>#include <map>#include <set>#include <queue>#include <vector>#define mem(a) memset(a, 0, sizeof(a))using namespace std;typedef pair<int, int> Pii;typedef long long LL;const int MAXN = 1005;const int inf = 0x3f3f3f3f;const int Mod = 100000000;inline int read(){    int f=1, x=0;    char ch = getchar();    while(ch<'0'||ch>'9')    {        if(ch=='-') f=-1;        ch=getchar();    }    while(ch>='0'&&ch<='9')    {        x=x*10+ch-'0';        ch=getchar();    }    return f*x;}struct node{   int w, v;}a[MAXN];bool cmp(node a, node b){    return a.v>b.v;}int n, m, k;int dp[MAXN];bool judge(int mid){    mem(dp);    for(int i=1;i<=n;++i)    {        if(a[i].v<mid)continue;//如果排过序，就break;        for(int j=m;j>=a[i].w;--j)                 dp[j]=max(dp[j], dp[j-a[i].w]+a[i].v);    }   if(dp[m]>=k)return true;    return false;}int main(){    while(~scanf("%d %d %d", &n, &m, &k))    {        for(int i=1;i<=n;++i)            scanf("%d %d", &a[i].w, &a[i].v);        int l=0, r=1000005;        int ans=-1;        //sort(a+1, a+1+n, cmp);        while(l<=r)        {            int mid= (l + r)>>1;            if(judge(mid))            {                ans=mid;                l=mid+1;            }            else                r=mid-1;        }        printf("%d\n", ans);        /*        while(l<=r)        {            int mid= (l + r)>>1;            if(judge(mid))                l=mid+1;            else                r=mid-1;        }        printf("%d\n", r);        */    }    return 0;}