poj 3258 River Hopscotch

最小值的最大化问题！！！二分搞定……

代码如下：

 

#include<iostream>
#include<stdio.h>
#include<algorithm>
#include<iomanip>
#include<cmath>
#include<cstring>
#include<vector>
#define ll __int64
#define pi acos(-1.0)
#define MAX 50000
using namespace std;
int an[100005];
int main(){
    int n,m,i,sum,left,right=0,mid,t;
    while(cin>>right>>n>>m){
        an[0] = 0;
        an[n+1] = right;
        for (i=1;i<=n;i++)
            cin>>an[i];
        sort(an,an+n+1);
        left = 0;
        for (i=0;i<=n;i++){
            an[i] = an[i+1]-an[i];
            if (left > an[i]) left = an[i];
        }
        while (left<=right){
            mid = (left+right)/2;
            sum = 0;t = 0;
            for (i=0;i<n;i++){
                if (sum+an[i]<mid){
                    sum += an[i];
                    t++;
                }
                else {
                    sum = 0;
                }
            }
            if (t>m){//t>m,说明m取大了
                right = mid-1;
            }
            else{
                left = mid+1;
            }
        }
        cout<<right<<endl;
    }
    return 0;
}