Square Problem

最新推荐文章于 2021-10-23 19:40:39 发布

原创最新推荐文章于 2021-10-23 19:40:39 发布 · 428 阅读

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CC 4.0 BY-SA版权

本文探讨了一种算法，旨在判断给定长度的棍子是否能组成正方形。通过分配棍子到正方形的四条边并计算每条边的总长度来实现。核心在于检查所有棍子分配后的边长是否相等。

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Problem Description: Given a set of sticks of various lengths, is it possible to join them end-to-end to form a square?

Input:

4 1 1 1 1

5 10 20 30 40 50

8 1 7 2 6 4 4 3 5

Output

Yes

Problem Analysis:

This problem is the assignment of the i-th stick to corresponding edges. Since there are 4 edges in the square, therefore, we can assign the stick to each edge of the square. When all sticks are judged, we will compute the length of each edge. Based on such thought, corresponding implement

#include <stdio.h>
#include<string.h>
long long a[1005];
long long b[1005];
int n;
int sum;
int flag=0;
void Init(){
	int i;
	scanf("%d",&n);
    for(i=0;i<n;i++){
        scanf("%lld",&a[i]);
        sum+=a[i];
    }
}
void traceback(int t){
    int i;
    if(flag)
    	return ;
    if(t==n){
        for(i=1;i<4;i++)
            if(b[i]!=sum)
       		 	return;
        flag=1;
        printf("yes");
        return ;
    }
 
    for(i=0;i<4;i++){
        b[i]+=a[t];
        if(b[i]<=sum)
            traceback(t+1);
        b[i]-=a[t];
    }
}
 
int main()
{
    int i;
    sum=0;
   	Init(); 
    if(sum%4){
        printf("no");
        return 0;
    } 
    sum=sum/4;
    memset(b,0,sizeof(b));
    traceback(0);
   if(!flag)
        printf("no");
    return 0;
}

is tabulated as follows