My Blog List

Friday, July 8, 2016

cutting a rod

I studied cuttingrod dp alogorithm.

first cuttingrod is recursive function
cuttingRodDP is dynamic problem.

If we want to use by using recursive function
to speed up. we have to use memoized array

def cuttingRod(s, arr):

    m = arr[s-1]
    for i in range(1,int(s/2)+1):
        left=  i
        right =s-i
        val = cuttingRod(left, arr) + cuttingRod(right,arr)
        print(left, right, val)
        m= max(m, val )

    return m

def cuttingRodDP(s, arr):

    m = [0 for i in range(len(arr)+1)]
    for i in range(1, len(arr)+1):
        m[i]= arr[i-1]

    maxValue =0
    for i in range(1, len(arr)+1):
        for j in range(1,i+1):
           maxValue =  max(maxValue, m[j] + m[i-j])
        m[i] = maxValue

    return maxValue

arr= [ 1 ,  5,   8 ,  9 , 10,  17,  17,  20]
print(cuttingRod(len(arr), arr))

print(cuttingRodDP(len(arr), arr))

No comments:

Post a Comment