## 题目描述：

LeetCode 640. Solve the Equation

Solve a given equation and return the value of `x` in the form of string "x=#value". The equation contains only '+', '-' operation, the variable `x` and its coefficient.

If there is no solution for the equation, return "No solution".

If there are infinite solutions for the equation, return "Infinite solutions".

If there is exactly one solution for the equation, we ensure that the value of `x` is an integer.

Example 1:

```Input: "x+5-3+x=6+x-2"
Output: "x=2"
```

Example 2:

```Input: "x=x"
Output: "Infinite solutions"
```

Example 3:

```Input: "2x=x"
Output: "x=0"
```

Example 4:

```Input: "2x+3x-6x=x+2"
Output: "x=-1"
```

Example 5:

```Input: "x=x+2"
Output: "No solution"
```

## 解题思路：

```用'='将等式分为左右两半

## Python代码：

``````class Solution(object):
def solveEquation(self, equation):
"""
:type equation: str
:rtype: str
"""
left, right = equation.split('=')
lx, lc = self.solve(left)
rx, rc = self.solve(right)
x, c = lx - rx, rc - lc
if x: return 'x=%d' % (c / x)
elif c: return 'No solution'
return 'Infinite solutions'

def solve(self, expr):
x = c = 0
num, sig = '', 1
for ch in expr + '#':
if '0' <= ch <= '9':
num += ch
elif ch == 'x':
x += int(num or '1') * sig
num, sig = '', 1
else:
c += int(num or '0') * sig
num, sig = '', 1
if ch == '-': sig = -1
return x, c
``````

Pingbacks已关闭。