B - Lever
Description
You have a description of a lever as string s. We'll represent the string length as record |s|, then the lever looks as a horizontal bar with weights of length |s| - 1 with exactly one pivot. We will assume that the bar is a segment on the Ox axis between points 0 and |s| - 1.
The decoding of the lever description is given below.
- If the i-th character of the string equals "^", that means that at coordinate i there is the pivot under the bar.
- If the i-th character of the string equals "=", that means that at coordinate i there is nothing lying on the bar.
- If the i-th character of the string equals digit c (1-9), that means that at coordinate i there is a weight of mass c on the bar.
Your task is, given the lever description, print if it will be in balance or not. Assume that the bar doesn't weight anything. Assume that the bar initially is in balance then all weights are simultaneously put on it. After that the bar either tilts to the left, or tilts to the right, or is in balance.
Input
The first line contains the lever description as a non-empty string s(3 ≤ |s| ≤ 106), consisting of digits (1-9) and characters "^" and "=". It is guaranteed that the line contains exactly one character "^". It is guaranteed that the pivot of the lever isn't located in any end of the lever bar.
To solve the problem you may need 64-bit integer numbers. Please, do not forget to use them in your programs.
Output
Print "left" if the given lever tilts to the left, "right" if it tilts to the right and "balance", if it is in balance.
Sample Input
Input
=^==
Output
balance
Input
9===^==1
Output
left
Input
2==^7==
Output
right
Input
41^52==
Output
balance分析：这道题看懂以后就是一道物理题，杠杆原理，相比大家都还记得把，力臂*力矩的问题，很明显，如果哪边重了就肯定要倾斜。下面给出这道题的代码。参考代码如下：#include<iostream>
#include<cstdio>
#include<cmath>
using namespace std;
int main()
{
char s[1000008];
int i, j, L1 = 1, L2 = 1;
long long a1 = 0, a2 = 0;
scanf("%s", s);
for(i=0;s[i]!='\n';i++)
{
if(s[i]=='^')
{
break;
}
}
j = i;
for(i=j-1;i>=0;i--)
{
if(s[i]!='=')
{
a1+=(s[i]-48)*L1;
}
L1++;
}
for (i=j+1;s[i]!='\0';i++)
{
if(s[i]!='=')
{
a2+=(s[i]-48)*L2;
}
L2++;
}
if (a1>a2)
{
printf("left\n");
}
else if (a1<a2)
{
printf("right\n");
}
else
{
printf("balance\n");
}
return 0;
}