Comments on: Find the missing number http://cstechie.com/find-the-missing-number/ Just another WordPress weblog Fri, 10 Sep 2010 20:28:05 -0600 http://wordpress.org/?v=2.8.5 hourly 1 By: syam http://cstechie.com/find-the-missing-number/comment-page-1/#comment-7 syam Sat, 07 Nov 2009 06:18:49 +0000 http://cstechie.com/?p=55#comment-7 Problem 1: Find sum of numbers from 1 to 1000 = 1000*1001/2 =500500 Add the current array sum of 999 numbers = S The missing number = 500500-S Problem 2: Find the sum of numbers from 1 to 1000 = 1000*1001/2 = 500500 = S Find sum of squares of numbers from 1 to 1000 = n*(n+1)*(2n+1)/6 = 333 833 500 = SS Find sum of 998 distinct numbers as N Find sum of squares of 998 distinct numbers as NS Let a and b be 2 missing numbers S-N=a+b SS-NS=a^2+b^2 Solve for a and b. Problem 1:
Find sum of numbers from 1 to 1000 = 1000*1001/2 =500500
Add the current array sum of 999 numbers = S
The missing number = 500500-S

Problem 2:
Find the sum of numbers from 1 to 1000 = 1000*1001/2 = 500500 = S
Find sum of squares of numbers from 1 to 1000 = n*(n+1)*(2n+1)/6 = 333 833 500 = SS
Find sum of 998 distinct numbers as N
Find sum of squares of 998 distinct numbers as NS
Let a and b be 2 missing numbers
S-N=a+b
SS-NS=a^2+b^2
Solve for a and b.

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