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Commit48017b9

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refactor 312
1 parentcf6edfd commit48017b9

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2 files changed

+60
-15
lines changed

2 files changed

+60
-15
lines changed

‎src/main/java/com/fishercoder/solutions/_312.java

Lines changed: 27 additions & 15 deletions
Original file line numberDiff line numberDiff line change
@@ -3,27 +3,39 @@
33
publicclass_312 {
44

55
publicstaticclassSolution1 {
6-
publicintmaxCoins(int[]iNums) {
7-
int[]nums =newint[iNums.length +2];
6+
/**
7+
* credit: https://leetcode.com/problems/burst-balloons/discuss/76228/Share-some-analysis-and-explanations
8+
* <p>
9+
* Divide and conquer with memoization
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*/
11+
publicintmaxCoins(int[]nums) {
12+
int[]input =newint[nums.length +2];
813
intn =1;
9-
for (intx :iNums) {
14+
for (intx :nums) {
1015
if (x >0) {
11-
nums[n++] =x;
16+
input[n++] =x;
1217
}
1318
}
14-
nums[0] =nums[n++] =1;
19+
input[0] =1;
20+
input[n++] =1;
1521

16-
int[][]dp =newint[n][n];
17-
for (intk =2;k <n; ++k) {
18-
for (intleft =0;left <n -k; ++left) {
19-
intright =left +k;
20-
for (inti =left +1;i <right; ++i) {
21-
dp[left][right] =Math.max(dp[left][right],
22-
nums[left] *nums[i] *nums[right] +dp[left][i] +dp[i][right]);
23-
}
24-
}
22+
int[][]memo =newint[n][n];
23+
returnburst(memo,input,0,n -1);
24+
}
25+
26+
privateintburst(int[][]memo,int[]nums,intleft,intright) {
27+
if (left +1 ==right) {
28+
return0;
29+
}
30+
if (memo[left][right] >0) {
31+
returnmemo[left][right];
32+
}
33+
intans =0;
34+
for (inti =left +1;i <right;i++) {
35+
ans =Math.max(ans,nums[left] *nums[i] *nums[right] +burst(memo,nums,left,i) +burst(memo,nums,i,right));
2536
}
26-
returndp[0][n -1];
37+
memo[left][right] =ans;
38+
returnans;
2739
}
2840
}
2941
}
Lines changed: 33 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,33 @@
1+
packagecom.fishercoder;
2+
3+
importcom.fishercoder.solutions._312;
4+
importorg.junit.BeforeClass;
5+
importorg.junit.Test;
6+
7+
importstaticorg.junit.Assert.assertEquals;
8+
9+
publicclass_312Test {
10+
privatestatic_312.Solution1solution1;
11+
privatestaticint[]nums;
12+
privatestaticintexpected;
13+
14+
@BeforeClass
15+
publicstaticvoidsetup() {
16+
solution1 =new_312.Solution1();
17+
}
18+
19+
@Test
20+
publicvoidtest1() {
21+
nums =newint[]{3,1,5,8};
22+
expected =167;
23+
assertEquals(expected,solution1.maxCoins(nums));
24+
}
25+
26+
@Test
27+
publicvoidtest2() {
28+
nums =newint[]{1,5};
29+
expected =10;
30+
assertEquals(expected,solution1.maxCoins(nums));
31+
}
32+
33+
}

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