From fc37d3163e633b1a2a36307d5cbcf221f9dd36f7 Mon Sep 17 00:00:00 2001
From: Valentyn Kolesnikov <javadev75@gmail.com>
Date: Tue, 29 Apr 2025 07:20:20 +0300
Subject: [PATCH 1/5] Improved tasks 3510, 3515
---
.../Solution.java | 168 ++++++++---------
.../Solution.java | 173 ++++++++++--------
2 files changed, 179 insertions(+), 162 deletions(-)
diff --git a/src/main/java/g3501_3600/s3510_minimum_pair_removal_to_sort_array_ii/Solution.java b/src/main/java/g3501_3600/s3510_minimum_pair_removal_to_sort_array_ii/Solution.java
index 9cd72b7a9..440f5587b 100644
--- a/src/main/java/g3501_3600/s3510_minimum_pair_removal_to_sort_array_ii/Solution.java
+++ b/src/main/java/g3501_3600/s3510_minimum_pair_removal_to_sort_array_ii/Solution.java
@@ -1,104 +1,104 @@
package g3501_3600.s3510_minimum_pair_removal_to_sort_array_ii;
// #Hard #Array #Hash_Table #Heap_Priority_Queue #Simulation #Linked_List #Ordered_Set
-// #Doubly_Linked_List #2025_04_09_Time_289_ms_(99.58%)_Space_82.88_MB_(17.23%)
+// #Doubly_Linked_List #2025_04_29_Time_274_ms_(98.94%)_Space_70.73_MB_(69.15%)
-public class Solution {
- private static class Segment {
- private final int start;
- private final int end;
- private Segment left;
- private Segment right;
- private int lIdx;
- private long lNum;
- private int rIdx;
- private long rNum;
- private boolean ok;
- private long minSum;
- private int li;
- private int ri;
+import java.util.Arrays;
- public static Segment init(int[] arr) {
- return new Segment(arr, 0, arr.length - 1);
+public class Solution {
+ public int minimumPairRemoval(int[] nums) {
+ if (nums.length == 1) {
+ return 0;
}
-
- public Segment(int[] arr, int s, int e) {
- start = s;
- end = e;
- if (s >= e) {
- lIdx = rIdx = s;
- lNum = rNum = arr[s];
- minSum = Long.MAX_VALUE;
- ok = true;
- return;
+ int size = (int) Math.pow(2, Math.ceil(Math.log(nums.length - 1) / Math.log(2)));
+ long[] segment = new long[size * 2 - 1];
+ Arrays.fill(segment, Long.MAX_VALUE);
+ int[] lefts = new int[size * 2 - 1];
+ int[] rights = new int[size * 2 - 1];
+ long[] sums = new long[nums.length];
+ Arrays.fill(sums, Long.MAX_VALUE / 2);
+ int[][] arrIdxToSegIdx = new int[nums.length][];
+ boolean[] isDecs = new boolean[nums.length];
+ sums[0] = nums[0];
+ int count = 0;
+ arrIdxToSegIdx[0] = new int[] {-1, size - 1};
+ for (int i = 1; i < nums.length; i++) {
+ if (nums[i] < nums[i - 1]) {
+ isDecs[i] = true;
+ count++;
}
- int mid = s + ((e - s) >> 1);
- left = new Segment(arr, s, mid);
- right = new Segment(arr, mid + 1, e);
- merge();
+ lefts[size + i - 2] = i - 1;
+ rights[size + i - 2] = i;
+ segment[size + i - 2] = nums[i - 1] + nums[i];
+ arrIdxToSegIdx[i] = new int[] {size + i - 2, size + i - 1};
+ sums[i] = nums[i];
}
-
- private void merge() {
- lIdx = left.lIdx;
- lNum = left.lNum;
- rIdx = right.rIdx;
- rNum = right.rNum;
- ok = left.ok && right.ok && left.rNum <= right.lNum;
- minSum = left.minSum;
- li = left.li;
- ri = left.ri;
- if (left.rNum + right.lNum < minSum) {
- minSum = left.rNum + right.lNum;
- li = left.rIdx;
- ri = right.lIdx;
- }
- if (right.minSum < minSum) {
- minSum = right.minSum;
- li = right.li;
- ri = right.ri;
- }
+ arrIdxToSegIdx[nums.length - 1][1] = -1;
+ for (int i = size - 2; i >= 0; i--) {
+ int l = 2 * i + 1;
+ int r = 2 * i + 2;
+ segment[i] = Math.min(segment[l], segment[r]);
}
-
- public void update(int i, long n) {
- if (start <= i && end >= i) {
- if (start >= end) {
- lNum = rNum = n;
+ int res = 0;
+ while (count > 0) {
+ int segIdx = 0;
+ while (2 * segIdx + 1 < segment.length) {
+ int l = 2 * segIdx + 1;
+ int r = 2 * segIdx + 2;
+ if (segment[l] <= segment[r]) {
+ segIdx = l;
} else {
- left.update(i, n);
- right.update(i, n);
- merge();
+ segIdx = r;
}
}
- }
-
- public Segment remove(int i) {
- if (start > i || end < i) {
- return this;
- } else if (start >= end) {
- return null;
+ int arrIdxL = lefts[segIdx];
+ int arrIdxR = rights[segIdx];
+ long numL = sums[arrIdxL];
+ long numR = sums[arrIdxR];
+ if (numL > numR) {
+ count--;
}
- left = left.remove(i);
- right = right.remove(i);
- if (null == left) {
- return right;
- } else if (null == right) {
- return left;
+ long newSum = sums[arrIdxL] = sums[arrIdxL] + sums[arrIdxR];
+ int[] leftPointer = arrIdxToSegIdx[arrIdxL];
+ int[] rightPointer = arrIdxToSegIdx[arrIdxR];
+ int prvSegIdx = leftPointer[0];
+ int nextSegIdx = rightPointer[1];
+ leftPointer[1] = nextSegIdx;
+ if (prvSegIdx != -1) {
+ int l = lefts[prvSegIdx];
+ if (sums[l] > numL && sums[l] <= newSum) {
+ count--;
+ } else if (sums[l] <= numL && sums[l] > newSum) {
+ count++;
+ }
+ modify(segment, prvSegIdx, sums[l] + newSum);
+ }
+ if (nextSegIdx != -1) {
+ int r = rights[nextSegIdx];
+ if (numR > sums[r] && newSum <= sums[r]) {
+ count--;
+ } else if (numR <= sums[r] && newSum > sums[r]) {
+ count++;
+ }
+ modify(segment, nextSegIdx, newSum + sums[r]);
+ lefts[nextSegIdx] = arrIdxL;
}
- merge();
- return this;
+ modify(segment, segIdx, Long.MAX_VALUE);
+ res++;
}
+ return res;
}
- public int minimumPairRemoval(int[] nums) {
- Segment root = Segment.init(nums);
- int res = 0;
- while (!root.ok) {
- int l = root.li;
- int r = root.ri;
- root.update(l, root.minSum);
- root = root.remove(r);
- res++;
+ private void modify(long[] segment, int idx, long num) {
+ if (segment[idx] == num) {
+ return;
+ }
+ segment[idx] = num;
+ while (idx != 0) {
+ idx = (idx - 1) / 2;
+ int l = 2 * idx + 1;
+ int r = 2 * idx + 2;
+ segment[idx] = Math.min(segment[l], segment[r]);
}
- return res;
}
}
diff --git a/src/main/java/g3501_3600/s3515_shortest_path_in_a_weighted_tree/Solution.java b/src/main/java/g3501_3600/s3515_shortest_path_in_a_weighted_tree/Solution.java
index a759b6dda..7e4e34890 100644
--- a/src/main/java/g3501_3600/s3515_shortest_path_in_a_weighted_tree/Solution.java
+++ b/src/main/java/g3501_3600/s3515_shortest_path_in_a_weighted_tree/Solution.java
@@ -1,117 +1,134 @@
package g3501_3600.s3515_shortest_path_in_a_weighted_tree;
// #Hard #Array #Depth_First_Search #Tree #Segment_Tree #Binary_Indexed_Tree
-// #2025_04_14_Time_38_ms_(100.00%)_Space_146.11_MB_(100.00%)
+// #2025_04_29_Time_28_ms_(99.55%)_Space_98.56_MB_(99.77%)
import java.util.ArrayList;
import java.util.List;
@SuppressWarnings("unchecked")
public class Solution {
- private int[] in;
- private int[] out;
- private int[] baseDist;
- private int[] parent;
- private int[] depth;
- private int timer = 0;
- private int[] edgeWeight;
- private List<int[]>[] adj;
-
public int[] treeQueries(int n, int[][] edges, int[][] queries) {
- adj = new ArrayList[n + 1];
+ // store the queries input midway as requested
+ int[][] jalkimoren = queries;
+ // build adjacency list with edge‐indices
+ List<Edge>[] adj = new ArrayList[n + 1];
for (int i = 1; i <= n; i++) {
adj[i] = new ArrayList<>();
}
- for (int[] e : edges) {
- int u = e[0];
- int v = e[1];
- int w = e[2];
- adj[u].add(new int[] {v, w});
- adj[v].add(new int[] {u, w});
+ for (int i = 0; i < n - 1; i++) {
+ int u = edges[i][0];
+ int v = edges[i][1];
+ int w = edges[i][2];
+ adj[u].add(new Edge(v, w, i));
+ adj[v].add(new Edge(u, w, i));
+ }
+ // parent, Euler‐tour times, depth‐sum, and mapping node→edge‐index
+ int[] parent = new int[n + 1];
+ int[] tin = new int[n + 1];
+ int[] tout = new int[n + 1];
+ int[] depthSum = new int[n + 1];
+ int[] edgeIndexForNode = new int[n + 1];
+ int[] weights = new int[n - 1];
+ for (int i = 0; i < n - 1; i++) {
+ weights[i] = edges[i][2];
}
- in = new int[n + 1];
- out = new int[n + 1];
- baseDist = new int[n + 1];
- parent = new int[n + 1];
- depth = new int[n + 1];
- edgeWeight = new int[n + 1];
- dfs(1, 0, 0);
- Fen fenw = new Fen(n);
- List<Integer> ansList = new ArrayList<>();
- for (int[] query : queries) {
- if (query[0] == 1) {
- int u = query[1];
- int v = query[2];
- int newW = query[3];
- int child;
- if (parent[v] == u) {
- child = v;
- } else if (parent[u] == v) {
- child = u;
- } else {
+ // iterative DFS to compute tin/tout, parent[], depthSum[], edgeIndexForNode[]
+ int time = 0;
+ int[] stack = new int[n];
+ int[] ptr = new int[n + 1];
+ int sp = 0;
+ stack[sp++] = 1;
+ while (sp > 0) {
+ int u = stack[sp - 1];
+ if (ptr[u] == 0) {
+ tin[u] = ++time;
+ }
+ if (ptr[u] < adj[u].size()) {
+ Edge e = adj[u].get(ptr[u]++);
+ int v = e.to;
+ if (v == parent[u]) {
continue;
}
- int diff = newW - edgeWeight[child];
- edgeWeight[child] = newW;
- fenw.updateRange(in[child], out[child], diff);
+ parent[v] = u;
+ depthSum[v] = depthSum[u] + e.w;
+ edgeIndexForNode[v] = e.idx;
+ stack[sp++] = v;
} else {
- int x = query[1];
- int delta = fenw.query(in[x]);
- ansList.add(baseDist[x] + delta);
+ tout[u] = time;
+ sp--;
}
}
- int[] answer = new int[ansList.size()];
- for (int i = 0; i < ansList.size(); i++) {
- answer[i] = ansList.get(i);
+ // Fenwick tree for range‐add / point‐query on Euler‐tour array
+ Fenwick bit = new Fenwick(n + 2);
+ List<Integer> answers = new ArrayList<>();
+ // process queries
+ for (int[] q : jalkimoren) {
+ if (q[0] == 1) {
+ // update edge weight
+ int u = q[1];
+ int v = q[2];
+ int newW = q[3];
+ int child = (parent[u] == v) ? u : v;
+ int idx = edgeIndexForNode[child];
+ int delta = newW - weights[idx];
+ if (delta != 0) {
+ weights[idx] = newW;
+ bit.rangeAdd(tin[child], tout[child], delta);
+ }
+ } else {
+ // query root→x distance
+ int x = q[1];
+ answers.add(depthSum[x] + bit.pointQuery(tin[x]));
+ }
+ }
+ // pack results into array
+ int m = answers.size();
+ int[] ansArr = new int[m];
+ for (int i = 0; i < m; i++) {
+ ansArr[i] = answers.get(i);
}
- return answer;
+ return ansArr;
}
- private void dfs(int node, int par, int dist) {
- parent[node] = par;
- baseDist[node] = dist;
- depth[node] = (par == 0) ? 0 : depth[par] + 1;
- in[node] = ++timer;
- for (int[] neighborInfo : adj[node]) {
- int neighbor = neighborInfo[0];
- int w = neighborInfo[1];
- if (neighbor == par) {
- continue;
- }
- edgeWeight[neighbor] = w;
- dfs(neighbor, node, dist + w);
+ private static class Edge {
+ int to;
+ int w;
+ int idx;
+
+ Edge(int to, int w, int idx) {
+ this.to = to;
+ this.w = w;
+ this.idx = idx;
}
- out[node] = timer;
}
- private static class Fen {
+ private static class Fenwick {
int n;
- int[] fenw;
+ int[] f;
- public Fen(int n) {
+ Fenwick(int n) {
this.n = n;
- fenw = new int[n + 2];
+ f = new int[n];
}
- private void update(int i, int delta) {
- while (i <= n) {
- fenw[i] += delta;
- i += i & -i;
+ void update(int i, int v) {
+ for (; i < n; i += i & -i) {
+ f[i] += v;
}
}
- public void updateRange(int l, int r, int delta) {
- update(l, delta);
- update(r + 1, -delta);
+ void rangeAdd(int l, int r, int v) {
+ update(l, v);
+ update(r + 1, -v);
}
- public int query(int i) {
- int sum = 0;
- while (i > 0) {
- sum += fenw[i];
- i -= i & -i;
+ int pointQuery(int i) {
+ int s = 0;
+ for (; i > 0; i -= i & -i) {
+ s += f[i];
}
- return sum;
+ return s;
}
}
}
From f35e25c067532d18b2c1b89e0216bd8a5f9e653e Mon Sep 17 00:00:00 2001
From: Valentyn Kolesnikov <javadev75@gmail.com>
Date: Tue, 29 Apr 2025 07:35:25 +0300
Subject: [PATCH 2/5] Fixed sonar
---
.../Solution.java | 16 ++++++++++++----
1 file changed, 12 insertions(+), 4 deletions(-)
diff --git a/src/main/java/g3501_3600/s3510_minimum_pair_removal_to_sort_array_ii/Solution.java b/src/main/java/g3501_3600/s3510_minimum_pair_removal_to_sort_array_ii/Solution.java
index 440f5587b..cf61c81ff 100644
--- a/src/main/java/g3501_3600/s3510_minimum_pair_removal_to_sort_array_ii/Solution.java
+++ b/src/main/java/g3501_3600/s3510_minimum_pair_removal_to_sort_array_ii/Solution.java
@@ -10,7 +10,7 @@ public int minimumPairRemoval(int[] nums) {
if (nums.length == 1) {
return 0;
}
- int size = (int) Math.pow(2, Math.ceil(Math.log(nums.length - 1) / Math.log(2)));
+ int size = (int) Math.pow(2, Math.ceil(Math.log(nums.length - 1.0) / Math.log(2)));
long[] segment = new long[size * 2 - 1];
Arrays.fill(segment, Long.MAX_VALUE);
int[] lefts = new int[size * 2 - 1];
@@ -18,18 +18,16 @@ public int minimumPairRemoval(int[] nums) {
long[] sums = new long[nums.length];
Arrays.fill(sums, Long.MAX_VALUE / 2);
int[][] arrIdxToSegIdx = new int[nums.length][];
- boolean[] isDecs = new boolean[nums.length];
sums[0] = nums[0];
int count = 0;
arrIdxToSegIdx[0] = new int[] {-1, size - 1};
for (int i = 1; i < nums.length; i++) {
if (nums[i] < nums[i - 1]) {
- isDecs[i] = true;
count++;
}
lefts[size + i - 2] = i - 1;
rights[size + i - 2] = i;
- segment[size + i - 2] = nums[i - 1] + nums[i];
+ segment[size + i - 2] = nums[i - 1] + (long) nums[i];
arrIdxToSegIdx[i] = new int[] {size + i - 2, size + i - 1};
sums[i] = nums[i];
}
@@ -39,6 +37,16 @@ public int minimumPairRemoval(int[] nums) {
int r = 2 * i + 2;
segment[i] = Math.min(segment[l], segment[r]);
}
+ return getRes(count, segment, lefts, rights, sums, arrIdxToSegIdx);
+ }
+
+ private int getRes(
+ int count,
+ long[] segment,
+ int[] lefts,
+ int[] rights,
+ long[] sums,
+ int[][] arrIdxToSegIdx) {
int res = 0;
while (count > 0) {
int segIdx = 0;
From f6f87cf3a19fc670e549fef864b17926078581f8 Mon Sep 17 00:00:00 2001
From: Valentyn Kolesnikov <javadev75@gmail.com>
Date: Tue, 29 Apr 2025 07:45:09 +0300
Subject: [PATCH 3/5] Added tests
---
.../SolutionTest.java | 12 ++++++++++++
1 file changed, 12 insertions(+)
diff --git a/src/test/java/g3501_3600/s3510_minimum_pair_removal_to_sort_array_ii/SolutionTest.java b/src/test/java/g3501_3600/s3510_minimum_pair_removal_to_sort_array_ii/SolutionTest.java
index c6fde4200..5bcd10907 100644
--- a/src/test/java/g3501_3600/s3510_minimum_pair_removal_to_sort_array_ii/SolutionTest.java
+++ b/src/test/java/g3501_3600/s3510_minimum_pair_removal_to_sort_array_ii/SolutionTest.java
@@ -15,4 +15,16 @@ void minimumPairRemoval() {
void minimumPairRemoval2() {
assertThat(new Solution().minimumPairRemoval(new int[] {1, 2, 2}), equalTo(0));
}
+
+ @Test
+ void minimumPairRemoval3() {
+ assertThat(new Solution().minimumPairRemoval(new int[] {5, 2, 3, 1}), equalTo(2));
+ }
+
+ @Test
+ void minimumPairRemoval4() {
+ assertThat(
+ new Solution().minimumPairRemoval(new int[] {2, 2, -1, 3, -2, 2, 1, 1, 1, 0, -1}),
+ equalTo(9));
+ }
}
From 7c52280572b09a2a57f4069e04fc4c3648e321d9 Mon Sep 17 00:00:00 2001
From: Valentyn Kolesnikov <javadev75@gmail.com>
Date: Tue, 29 Apr 2025 07:46:43 +0300
Subject: [PATCH 4/5] Improved task
---
.../Solution.java | 5 +----
1 file changed, 1 insertion(+), 4 deletions(-)
diff --git a/src/main/java/g3501_3600/s3510_minimum_pair_removal_to_sort_array_ii/Solution.java b/src/main/java/g3501_3600/s3510_minimum_pair_removal_to_sort_array_ii/Solution.java
index cf61c81ff..c29a263b3 100644
--- a/src/main/java/g3501_3600/s3510_minimum_pair_removal_to_sort_array_ii/Solution.java
+++ b/src/main/java/g3501_3600/s3510_minimum_pair_removal_to_sort_array_ii/Solution.java
@@ -1,7 +1,7 @@
package g3501_3600.s3510_minimum_pair_removal_to_sort_array_ii;
// #Hard #Array #Hash_Table #Heap_Priority_Queue #Simulation #Linked_List #Ordered_Set
-// #Doubly_Linked_List #2025_04_29_Time_274_ms_(98.94%)_Space_70.73_MB_(69.15%)
+// #Doubly_Linked_List #2025_04_29_Time_278_ms_(98.94%)_Space_70.90_MB_(68.88%)
import java.util.Arrays;
@@ -98,9 +98,6 @@ private int getRes(
}
private void modify(long[] segment, int idx, long num) {
- if (segment[idx] == num) {
- return;
- }
segment[idx] = num;
while (idx != 0) {
idx = (idx - 1) / 2;
From ff1719f9958f1d5ea59c31f66aaa567af56f1bb2 Mon Sep 17 00:00:00 2001
From: Valentyn Kolesnikov <javadev75@gmail.com>
Date: Tue, 29 Apr 2025 07:50:23 +0300
Subject: [PATCH 5/5] Added test
---
.../Solution.java | 3 +++
.../SolutionTest.java | 5 +++++
2 files changed, 8 insertions(+)
diff --git a/src/main/java/g3501_3600/s3510_minimum_pair_removal_to_sort_array_ii/Solution.java b/src/main/java/g3501_3600/s3510_minimum_pair_removal_to_sort_array_ii/Solution.java
index c29a263b3..3f550f47e 100644
--- a/src/main/java/g3501_3600/s3510_minimum_pair_removal_to_sort_array_ii/Solution.java
+++ b/src/main/java/g3501_3600/s3510_minimum_pair_removal_to_sort_array_ii/Solution.java
@@ -98,6 +98,9 @@ private int getRes(
}
private void modify(long[] segment, int idx, long num) {
+ if (segment[idx] == num) {
+ return;
+ }
segment[idx] = num;
while (idx != 0) {
idx = (idx - 1) / 2;
diff --git a/src/test/java/g3501_3600/s3510_minimum_pair_removal_to_sort_array_ii/SolutionTest.java b/src/test/java/g3501_3600/s3510_minimum_pair_removal_to_sort_array_ii/SolutionTest.java
index 5bcd10907..f210f218c 100644
--- a/src/test/java/g3501_3600/s3510_minimum_pair_removal_to_sort_array_ii/SolutionTest.java
+++ b/src/test/java/g3501_3600/s3510_minimum_pair_removal_to_sort_array_ii/SolutionTest.java
@@ -27,4 +27,9 @@ void minimumPairRemoval4() {
new Solution().minimumPairRemoval(new int[] {2, 2, -1, 3, -2, 2, 1, 1, 1, 0, -1}),
equalTo(9));
}
+
+ @Test
+ void minimumPairRemoval5() {
+ assertThat(new Solution().minimumPairRemoval(new int[] {5}), equalTo(0));
+ }
}