HDU4004 The Frog's Games [二分]

　　一道简单的二分。

　　

#include <string.h>
#include <stdio.h>
#include <algorithm>
#define MAXN 500005
int l,n,m;
int d[MAXN];
int cant(int x){
    int now=0,ans=0;
    for(int i=1;i<=n;i++){
        if(d[i]-d[i-1]>x)return 1;
        if(d[i+1]-d[now]>x)now=i,ans++;
    }
    //最后一步要跳到终点
    if(now<n)ans++;
    return ans>m;
}
int main(){
    freopen("test.in","r",stdin);
    while(scanf("%d%d%d",&l,&n,&m)!=EOF){
        for(int i=1;i<=n;i++)scanf("%d",&d[i]);
        d[0]=0,d[++n]=l;
        std::sort(d,d+n+1);
        int low=0,high=l,mid;
        for(;;){
            mid=(low+high)>>1;
            if(mid==low)break;
            if(cant(mid))low=mid;
            else high=mid;
        }
        printf("%d\n",mid+1);
    }
    return 0;
}