1.1.3 algorithm

archives/01-introduction-to-computer-science-and-programming/archives/UNIT-01/03-problem-solving/lec03.py

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+"""
+# Find the cube root of a perfect cube
+x = int(raw_input('Enter an integer: '))
+ans = 0
+
+while ans * ans * ans < abs(x):
+  ans = ans + 1
+  # print 'current guess = ', ans
+
+if ans * ans * ans != abs(x):
+  print x, ' is not a perfect cube'
+else:
+  if x < 0:
+    ans = -ans
+  print 'Cube root of ' + str(x) + ' is ' + str(ans)
+"""
+
+"""
+# Find the cube root of a perfect cube
+x = int(raw_input('Enter an integer: '))
+for ans in range(0, abs(x) + 1):
+  if ans**3 == abs(x):
+    break
+if ans**3 != abs(x):
+  print x, ' is not a perfect cube'
+else:
+  if x < 0:
+    ans = -ans
+  print 'Cube root of ' + str(x) + ' is ' + str(ans)
+"""
+
+"""
+x = 25000
+epsilon = 0.01
+numGuesses = 0
+ans = 0.0
+
+while abs(ans**2 - x) >= epsilon and ans <= x:
+  ans += 0.00001
+  numGuesses += 1
+
+print 'numGuesses = ', numGuesses
+
+if abs(ans**2 - x) >= epsilon:
+  print 'Failed on square root of ', x
+else:
+  print ans, ' is close to square root of ', x
+"""
+
+x = 12345
+epsilon = 0.01
+numGuesses = 0
+low = 0.0
+high = x
+ans = (high + low) / 2.0
+
+while abs(ans ** 2 - x) >= epsilon and ans <= x:
+  #print low, high, ans
+  numGuesses += 1
+  if ans ** 2 < x:
+    low = ans
+  else:
+    high = ans
+  ans = (high + low) / 2.0
+
+print 'numGuesses = ', numGuesses
+print ans, ' is close to square root of ', x