PAT 1046 Shortest Distance

该博客主要讨论了一种环形路线中计算两点间最短距离的问题。给定一个圆环上的点,每个点到其相邻点的距离已知,程序通过输入的数据计算任意两点间的最短路径,考虑了顺时针和逆时针方向的两种情况,输出最小距离。此问题涉及到路径规划和最优化算法的应用。

题目描述

在这里插入图片描述

分析:

求最短距离,但是每个点只能到达相邻点,dis[i]表示1号点按顺时针方向到达i号点顺时针方向的下一个点的距离,sum表示一圈的总距离,对于每次查询,比较dis(left,right)和sum-(left,right),取最小值

#include<cstdio>
#include<algorithm>
using namespace std;

int dis[100005];
int main(){
	int sum=0;
	int n,x;
	scanf("%d",&n);
	for(int i=1;i<=n;i++){
		scanf("%d",&x);
		sum+=x;
		dis[i]=sum;
	}
	int query;
	scanf("%d",&query);
	int left,right;
	while(query--){
		scanf("%d%d",&left,&right);
		if(left>right){
			swap(left,right);
		}
		printf("%d\n",min(dis[right-1]-dis[left-1],sum-(dis[right-1]-dis[left-1])));
	}
}
Every year the cows hold an event featuring a peculiar version of hopscotch that involves carefully jumping from rock to rock in a river. The excitement takes place on a long, straight river with a rock at the start and another rock at the end, L units away from the start (1 ≤ L ≤ 1,000,000,000). Along the river between the starting and ending rocks, N (0 ≤ N ≤ 50,000) more rocks appear, each at an integral distance Di from the start (0 < Di < L). To play the game, each cow in turn starts at the starting rock and tries to reach the finish at the ending rock, jumping only from rock to rock. Of course, less agile cows never make it to the final rock, ending up instead in the river. Farmer John is proud of his cows and watches this event each year. But as time goes by, he tires of watching the timid cows of the other farmers limp across the short distances between rocks placed too closely together. He plans to remove several rocks in order to increase the shortest distance a cow will have to jump to reach the end. He knows he cannot remove the starting and ending rocks, but he calculates that he has enough resources to remove up to M rocks (0 ≤ M ≤ N). FJ wants to know exactly how much he can increase the shortest distance *before* he starts removing the rocks. Help Farmer John determine the greatest possible shortest distance a cow has to jump after removing the optimal set of M rocks. Input Line 1: Three space-separated integers: L, N, and M Lines 2..N+1: Each line contains a single integer indicating how far some rock is away from the starting rock. No two rocks share the same position. Output Line 1: A single integer that is the maximum of the shortest distance a cow has to jump after removing M rocks Sample Inputcopy Outputcopy 25 5 2 2 14 11 21 17 4 Hint Before removing any rocks, the shortest jump was a jump of 2 from 0 (the start) to 2. After removing the rocks at 2 and 14, the shortest required jump is a jump of 4 (from 17 to 21 or from 21 to 25).
07-24
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