Largest value of the expression
package _interview_question /** * You are given a list of non-negative integers. * Find the largest value of the expression you can get by using +, * and ( ) operators. Example: Input: [1, 2, 1, 2] Output: 9 Explanation: (1 + 2) * (1 + 2) = 9 Follow-up: Negative values are allowed. * */ class Solution17 { /* * solution: DP, Top-Down, Time:O(n^2), Space:O(n^2) * */ fun largestValue(nums: IntArray): Int { if (nums == null || nums.isEmpty()) { return 0 } val n = nums.size val dp = Array(n) { IntArray(n) { Int.MIN_VALUE } } return help(nums, 0, n - 1, dp) } private fun help(nums: IntArray, l: Int, r: Int, dp: Array<IntArray>): Int { if (l == r) { return nums[l] } if (dp[l][r] != Int.MIN_VALUE) { return dp[l][r] } var result = 0 for (i in 0 until r - l) { /* * sum up and multiply each number one by one then find out the maximum value, for example:1,2,3,4: * 1+2,1+3,1+4,2+3,2+4... * */ result = Math.max(result, help(nums, l, l + i, dp) + help(nums, l + i + 1, r, dp)) result = Math.max(result, help(nums, l, l + i, dp) * help(nums, l + i + 1, r, dp)) } dp[l][r] = result return result } }