NOIP2010 完善程序 

2.（过河问题）

#include<iostream>
#include<cstring>
using namespace std;
const int SIZE=100,INFINITY = 10000;
const bool LEFT,RIGHT =false,LEFT_TO_RIGHT=true,RIGHT_TO_LEFT=false;
int n,hour[SIZE];
bool pos[SIZE];
int max(int a,int b) {
	if(a>b) return a;
	else return b;
}
int go(bool stage) {
	int i,j,num,tmp,ans;
	if(stage==RIGHT_TO_LEFT) {
		num=0;ans=0;
		for(i=1; i<=n; i++)
			if(pos[i]==RIGHT) {
				num++;
				if( hour[i]>ans)
					ans=hour[i];
			}
		if(         ①        )
			return ans;
		ans=INFINITY;
		for(i=1; i<=n-1; i++)
			if(pos[i]==RIGHT)
				for(j=i+1; j<=n; j++)
					if(pos[j]==RIGHT) {
						pos[i]=LEFT;
						pos[j]=LEFT;
						tmp=max(hour[i],hour[j])+         ②       ;
						if(tmp<ans)
							ans=tmp;
						pos[i]=RIGHT;
						pos[j]=RIGHT;

					}
		return ans;
	}
	if(stage==LEFT_TO_RIGHT) {
		ans=INFINITY;
		for(i=1; i<=n; i++)
			if(         ③        ) {
				pos[i]=RIGHT;
				tmp=        ④         ;
				if(tmp<ans)
					ans=tmp;
				⑤      ;
			}
		return ans;
	}
	return 0;
}
int main() {
	int i;
	cin>>n;
	for(i=1; i<=n; i++) {
		cin>>hour[i];
		pos[i]=RIGHT;
	}
	cout<<go[RIGHT_TO_LEFT)<<endl;
	return 0;
}