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add 849 java
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@yennanliu
yennanliu committed Dec 27, 2024
1 parent 0f1d7ec commit f9062de
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182 changes: 129 additions & 53 deletions leetcode_java/src/main/java/LeetCodeJava/Array/MaximizeDistanceToClosestPerson.java
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Original file line number Diff line number Diff line change
Expand Up @@ -53,69 +53,115 @@
*/
public class MaximizeDistanceToClosestPerson {

// V0
// TODO : fix below
// public int maxDistToClosest(int[] seats) {
//
// List<Integer> distances = new ArrayList<>();
// int lastIdx = -1;
// for(int i = seats.length - 1; i >= 0; i--){
// if (seats[i] == 1){
// if (lastIdx != -1){
// int diff = Math.abs(i - lastIdx);
// distances.add(diff);
// }
// lastIdx = i;
// }
// }
//
// System.out.println(">>> (before sort) distances = " + distances);
// distances.sort(Integer::compareTo);
// System.out.println(">>> (after sort) distances = " + distances);
//
// // edge case : if only one "1"
// if (distances.isEmpty()){
// return seats.length-1;
// }
// // return the max dist
// return distances.get(distances.size()-1) / 2; // ??
// }
// V0
// TODO : fix below
// public int maxDistToClosest(int[] seats) {
//
// List<Integer> distances = new ArrayList<>();
// int lastIdx = -1;
// for(int i = seats.length - 1; i >= 0; i--){
// if (seats[i] == 1){
// if (lastIdx != -1){
// int diff = Math.abs(i - lastIdx);
// distances.add(diff);
// }
// lastIdx = i;
// }
// }
//
// System.out.println(">>> (before sort) distances = " + distances);
// distances.sort(Integer::compareTo);
// System.out.println(">>> (after sort) distances = " + distances);
//
// // edge case : if only one "1"
// if (distances.isEmpty()){
// return seats.length-1;
// }
// // return the max dist
// return distances.get(distances.size()-1) / 2; // ??
// }

// V1-1
// IDEA : Next Array
// https://leetcode.com/problems/maximize-distance-to-closest-person/editorial/
public int maxDistToClosest_1_1(int[] seats) {
int N = seats.length;
int[] left = new int[N], right = new int[N];
Arrays.fill(left, N);
Arrays.fill(right, N);
// V0-1
// IDEA (fixed by gpt)
/**
* IDEA :
*
* Explanation of the Code:
* 1. Initial Setup:
* • lastOccupied keeps track of the index of the last seat occupied by a person.
* • maxDistance is initialized to 0 to store the maximum distance found.
*
* 2. Iterate Through the Array:
* • When a seat is occupied (seats[i] == 1):
* • If it’s the first occupied seat, calculate the distance from the start of the array to this seat (i).
* • Otherwise, calculate the middle distance between the current and the last occupied seat using (i - lastOccupied) / 2.
*
* 3. Check the Last Segment:
* • If the last seat is empty, calculate the distance from the last occupied seat to the end of the array (seats.length - 1 - lastOccupied).
*
* 4. Return the Maximum Distance:
* • The value of maxDistance at the end of the loop is the answer.
*
*
* Example :
* input : seats = [1, 0, 0, 0, 1, 0, 1]
*
* Execution Steps:
* 1. First occupied seat at index 0 → Distance to start = 0.
* 2. Second occupied seat at index 4 → Middle distance = (4 - 0) / 2 = 2.
* 3. Third occupied seat at index 6 → Middle distance = (6 - 4) / 2 = 1.
* 4. No empty seats after the last occupied seat.
* 5. maxDistance = 2.
*
* output: 2
*
*/
public int maxDistToClosest_0_1(int[] seats) {
int maxDistance = 0;
int lastOccupied = -1;

for (int i = 0; i < N; ++i) {
if (seats[i] == 1)
left[i] = 0;
else if (i > 0)
left[i] = left[i - 1] + 1;
// Traverse the array to calculate maximum distances
for (int i = 0; i < seats.length; i++) {
/** NOTE !!! handle the seat val == 1 cases */
if (seats[i] == 1) {
if (lastOccupied == -1) {
// Handle the case where the `first` occupied seat is found
maxDistance = i; // Distance from the start to the first occupied seat
} else {
// Calculate the distance to the closest person for the middle segment
/** NOTE !!! need to divided by 2, since the person need to seat at `middle` seat */
maxDistance = Math.max(maxDistance, (i - lastOccupied) / 2);
}
lastOccupied = i;
}
}

for (int i = N - 1; i >= 0; --i) {
if (seats[i] == 1)
right[i] = 0;
else if (i < N - 1)
right[i] = right[i + 1] + 1;
// Handle the case where the last segment is empty
if (seats[seats.length - 1] == 0) {
maxDistance = Math.max(maxDistance, seats.length - 1 - lastOccupied);
}

int ans = 0;
for (int i = 0; i < N; ++i)
if (seats[i] == 0)
ans = Math.max(ans, Math.min(left[i], right[i]));
return ans;
return maxDistance;
}


// V1-2
// V1-1
// IDEA : 2 POINTERS
// https://leetcode.com/problems/maximize-distance-to-closest-person/editorial/
public int maxDistToClosest_1_2(int[] seats) {
/**
* IDEA :
*
* In a group of K adjacent empty seats between two people, the answer is (K+1) / 2.
*
* Algorithm
*
* For each group of K empty seats between two people,
* we can take into account the candidate answer (K+1) / 2.
*
* For groups of empty seats between the edge of the row and one other person,
* the answer is K, and we should take into account those answers too.
*
*/
public int maxDistToClosest_1_1(int[] seats) {
int N = seats.length;
int prev = -1, future = 0;
int ans = 0;
Expand All @@ -136,5 +182,35 @@ public int maxDistToClosest_1_2(int[] seats) {
return ans;
}

// V1-2
// IDEA : Next Array
// https://leetcode.com/problems/maximize-distance-to-closest-person/editorial/
public int maxDistToClosest_1_2(int[] seats) {
int N = seats.length;
int[] left = new int[N], right = new int[N];
Arrays.fill(left, N);
Arrays.fill(right, N);

for (int i = 0; i < N; ++i) {
if (seats[i] == 1)
left[i] = 0;
else if (i > 0)
left[i] = left[i - 1] + 1;
}

for (int i = N - 1; i >= 0; --i) {
if (seats[i] == 1)
right[i] = 0;
else if (i < N - 1)
right[i] = right[i + 1] + 1;
}

int ans = 0;
for (int i = 0; i < N; ++i)
if (seats[i] == 0)
ans = Math.max(ans, Math.min(left[i], right[i]));
return ans;
}

// V2
}
65 changes: 40 additions & 25 deletions leetcode_java/src/main/java/dev/workspace7.java
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Original file line number Diff line number Diff line change
Expand Up @@ -8,37 +8,52 @@ public class workspace7 {
public static void main(String[] args) {

// ------------------- TEST 1
// int len = 5;
// int[][] updates ={ {1,3,2}, {2,4,3}, {0,2,-2} };
// int[] res = getModifiedArray(len, updates);
// System.out.println(">>> res = ");
// for (int x : res){
// // [-2,0,3,5,3]
// System.out.println(x);
// }
// int len = 5;
// int[][] updates ={ {1,3,2}, {2,4,3}, {0,2,-2} };
// int[] res = getModifiedArray(len, updates);
// System.out.println(">>> res = ");
// for (int x : res){
// // [-2,0,3,5,3]
// System.out.println(x);
// }

// ------------------- TEST 2
// int[][] mat1 = new int[][]{ {1,0,0}, {-1,0,3} };
// int[][] mat2 = new int[][]{ {7,0,0}, {0,0,0}, {0,0,1} };
// int[][] res = multiply(mat1, mat2);
// System.out.println(">>> res = ");
// for (int i = 0; i < res.length; i++){
// for (int j = 0; j < res[0].length; j++){
// System.out.println(res[i][j]);
// }
// }
// int[][] mat1 = new int[][]{ {1,0,0}, {-1,0,3} };
// int[][] mat2 = new int[][]{ {7,0,0}, {0,0,0}, {0,0,1} };
// int[][] res = multiply(mat1, mat2);
// System.out.println(">>> res = ");
// for (int i = 0; i < res.length; i++){
// for (int j = 0; j < res[0].length; j++){
// System.out.println(res[i][j]);
// }
// }

// ------------------- TEST 3
// String a = "a";
// String b = "b";
// a += b;
// System.out.println(">> a = " + a);
// String a = "a";
// String b = "b";
// a += b;
// System.out.println(">> a = " + a);

// ------------------- TEST 4
List<String> x = new ArrayList<>();
x.add("a");
x.add("b");
System.out.println(x.toString());
// List<String> x = new ArrayList<>();
// x.add("a");
// x.add("b");
// System.out.println(x.toString());

// ------------------- TEST 5
// ++i -> It increments i after the current iteration’s execution.
/**
* Key Points:
* • Prefix (++i) vs. Postfix (i++):
* • Prefix increments the value before use.
* • Postfix increments the value after use.
* • In a for loop, this distinction doesn’t matter since the increment happens at the end of each iteration.
* • Variable Name:
* • Ensure the loop variable is consistently referenced. Mixing i and I results in a compilation error due to case sensitivity in Java.
*/
for (int i = 0; i < 5; ++i) {
System.out.println(i);
}
}


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