Create solve-the-equation.py

kamyu104 · web-flow · commit 71c8e8e3d639 · 2017-07-20T23:56:39.000+08:00
diff --git a/Python/solve-the-equation.py b/Python/solve-the-equation.py
@@ -0,0 +1,44 @@
+# Time:  O(n)
+# Space: O(n)
+
+# 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"
+
+class Solution(object):
+    def solveEquation(self, equation):
+        """
+        :type equation: str
+        :rtype: str
+        """
+        a, b = 0, 0
+        side = 1
+        for eq, sign, num, isx in re.findall('(=)|([-+]?)(\d*)(x?)', equation):
+            if eq:
+                side = -1
+            elif isx:
+                a += side * int(sign + '1') * int(num or 1)
+            elif num:
+                b -= side * int(sign + num)
+        return 'x=%d' % (b / a) if a else 'No solution' if b else 'Infinite solutions'
