hdoj4004The Frog's Games

Problem Description

The annual Games in frogs' kingdom started again. The most famous game is the Ironfrog Triathlon. One test in the Ironfrog Triathlon is jumping. This project requires the frog athletes to jump over the river. The width of the river is L (1<= L <= 1000000000). There are n (0<= n <= 500000) stones lined up in a straight line from one side to the other side of the river. The frogs can only jump through the river, but they can land on the stones. If they fall into the river, they
are out. The frogs was asked to jump at most m (1<= m <= n+1) times. Now the frogs want to know if they want to jump across the river, at least what ability should they have. (That is the frog's longest jump distance).

 

Input

The input contains several cases. The first line of each case contains three positive integer L, n, and m.
Then n lines follow. Each stands for the distance from the starting banks to the nth stone, two stone appear in one place is impossible.

 

Output

For each case, output a integer standing for the frog's ability at least they should have.

 

Sample Input

6 1 2225 3 311 218

 

Sample Output

411
题意：一条河宽为l,河中有n块石头，青蛙想要过河，可以先跳在河中的石头上，再跳到对岸，但它只能跳m次，然后给出每块石头距河对岸的距离，问青蛙一次至少跳多少距离才能安全过河.
代码如下：
#include<cstdio>#include<cstring>#include<algorithm>using namespace std;int d[1001000];int mid,m,l,n,left,rig,ant;bool judge(int mid){int ans=0,i;int last=0;for(i=1;i<=n+1;){if(d[i]<=last+mid)i++;else{if(last==d[i-1])return false;last=d[i-1];ans++;}}ans++;return ans<=m;}int main(){while(scanf("%d%d%d",&l,&n,&m)!=EOF){int i;for(i=1;i<=n;i++)scanf("%d",&d[i]); d[n+1]=l;sort(d+1,d+n+1);left=1;rig=l;while(left<=rig){mid=(left+rig)/2;if(judge(mid)){ant=mid;rig=mid-1;}elseleft=mid+1;}printf("%d\n",ant);}}