POJ 3258 River Hopscotch 二分查找

题意：一条长为l（1~1,000,000,000）的河中，有n(1~50,000)块可垫脚的石头（不包括起始点和终点的），给出它们与起始点的距离rock[i]，现在要你移除其中的m块，使得具有最小间距的相邻两块石头之间的距离最大。

#include <stdio.h>
#include <iostream>
#include <algorithm>
using namespace std;
int cmp(const int &a,const int &b)
{
    return a<b;
}
int m,n,l;
int rock[50005];
int dis[50005];
int judge(int mid)
{
    int i;
    int len;
    int num;
    num = len = 0;
    for(i = 1;i <= n+1;i++)
    {
        if(len+dis[i] <= mid)
        len+=dis[i],num++;
        else
        len = 0;
    }

    if(num <= m)
    return 0;
    return 1;
}
int main()
{
    int i;
    while(cin>>l>>n>>m)
    {
        rock[0] = 0,rock[n+1] = l;
        for(i = 1;i <= n;i++)
        cin>>rock[i];
        sort(rock+1,rock+n+1,cmp);
        int low,high;
        low = l;
        high = l;
        for(i = 1;i <= n+1;i++)
        {
            dis[i] = rock[i]-rock[i-1];
            if(low > dis[i])
            low = dis[i];
        }

        int mid = (high+low)/2;

        while(low <= high)
        {
            if(judge(mid))
            high = mid-1;
            else
            low = mid+1;
            mid = (low+high)/2;
        }
        cout<<low<<endl;
    }
    return 0;
}