Given
n
balloons, indexed from 0
to n-1
. Each balloon is painted with a number on it represented by array nums
. You are asked to burst all the balloons. If the you burst balloon i
you will get nums[left] * nums[i] * nums[right]
coins. Here left
and right
are adjacent indices of i
. After the burst, the left
and right
then becomes adjacent.
Find the maximum coins you can collect by bursting the balloons wisely.
Note:
(1) You may imagine
(2) 0 ≤
(1) You may imagine
nums[-1] = nums[n] = 1
. They are not real therefore you can not burst them.(2) 0 ≤
n
≤ 500, 0 ≤ nums[i]
≤ 100
Example:
Given
[3, 1, 5, 8]
Return
167
nums = [3,1,5,8] --> [3,5,8] --> [3,8] --> [8] --> [] coins = 3*1*5 + 3*5*8 + 1*3*8 + 1*8*1 = 167
public class Solution {
public int maxCoins(int[] nums) {
if (nums == null || nums.length == 0) return 0;
int[][] dp = new int[nums.length][nums.length];
for (int len = 1; len <= nums.length; len++) {
for (int start = 0; start <= nums.length - len; start++) {
int end = start + len - 1;
for (int i = start; i <= end; i++) {
int coins = nums[i] * getValue(nums, start - 1) * getValue(nums, end + 1);
coins += i != start ? dp[start][i - 1] : 0; // If not first one, we can add subrange on its left.
coins += i != end ? dp[i + 1][end] : 0; // If not last one, we can add subrange on its right
dp[start][end] = Math.max(dp[start][end], coins);
}
}
}
return dp[0][nums.length - 1];
}
private int getValue(int[] nums, int i) { // Deal with num[-1] and num[num.length]
if (i < 0 || i >= nums.length) {
return 1;
}
return nums[i];
}
}
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