Special Problem

Author: rahulcode22

Math/primeNumberDifference.py

@@ -0,0 +1,35 @@
+'''
+Given two integers find the maximum difference between two prime numbers contained in their range. For e.g. if you are given two integers 2 and 6, i.e range [2,6] inclusive, the two farthest prime numbers are 2 & 5 and the answer is 3. If there are no prime numbers in the range, print 0.
+'''
+from bisect import bisect_left, bisect_right
+N = 10**6
+def getPrimes(N):
+    primes = [2]
+    check = [1] * N
+    for i in range(3,N,2):
+        if check[i]:
+            primes.append(i)
+            for j in range(3*i,N,2*i):
+                check[j] = 0
+    return primes
+
+primes = getPrimes(N)
+t = int(raw_input())
+for i in range(t):
+    n1, n2 = map(int,raw_input().split())
+    i1 = bisect_right(primes,n1)
+    i2 = bisect_left(primes,n2)
+    if i1 > 0 and primes[i1-1] == n1:
+        i1 -= 1
+    while i2 > 0 and primes[i2]  > n2:
+        i2 -= 1
+
+    if i2 + 1 < len(primes) and primes[i2+1] <= n2:
+        i2 += 1
+    p1 = primes[i1]
+    p2 = primes[i2]
+    #print p1, p2
+    if p1 < p2:
+        print p2-p1
+    else:
+        print 0