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Spiral Matrix II – LeetCode Solution Java , Python 3, Python 2 , C , C++, Best and Optimal Solutions , All you need.
Given a positive integer n, generate an n x n matrix filled with elements from 1 to n2 in spiral order.
Example 1:
Input: n = 3 Output: [[1,2,3],[8,9,4],[7,6,5]]
Example 2:
Input: n = 1 Output: [[1]]
Constraints:
1 <= n <= 20
C++ Spiral Matrix II LeetCode Solution
class Solution {
public:
vector<vector<int> > generateMatrix(int n) {
vector<vector<int> > ret( n, vector<int>(n) );
int k = 1, i = 0;
while( k <= n * n )
{
int j = i;
// four steps
while( j < n - i ) // 1. horizonal, left to right
ret[i][j++] = k++;
j = i + 1;
while( j < n - i ) // 2. vertical, top to bottom
ret[j++][n-i-1] = k++;
j = n - i - 2;
while( j > i ) // 3. horizonal, right to left
ret[n-i-1][j--] = k++;
j = n - i - 1;
while( j > i ) // 4. vertical, bottom to top
ret[j--][i] = k++;
i++; // next loop
}
return ret;
}
};
Java Spiral Matrix II LeetCode Solution
public class Solution {
public int[][] generateMatrix(int n) {
// Declaration
int[][] matrix = new int[n][n];
// Edge Case
if (n == 0) {
return matrix;
}
// Normal Case
int rowStart = 0;
int rowEnd = n-1;
int colStart = 0;
int colEnd = n-1;
int num = 1; //change
while (rowStart <= rowEnd && colStart <= colEnd) {
for (int i = colStart; i <= colEnd; i ++) {
matrix[rowStart][i] = num ++; //change
}
rowStart ++;
for (int i = rowStart; i <= rowEnd; i ++) {
matrix[i][colEnd] = num ++; //change
}
colEnd --;
for (int i = colEnd; i >= colStart; i --) {
if (rowStart <= rowEnd)
matrix[rowEnd][i] = num ++; //change
}
rowEnd --;
for (int i = rowEnd; i >= rowStart; i --) {
if (colStart <= colEnd)
matrix[i][colStart] = num ++; //change
}
colStart ++;
}
return matrix;
}
}
Python 3 Spiral Matrix II LeetCode Solution
def generateMatrix(self, n):
A, lo = [], n*n+1
while lo > 1:
lo, hi = lo - len(A), lo
A = [range(lo, hi)] + zip(*A[::-1])
return A
Array-1180
String-562
Hash Table-412
Dynamic Programming-390
Math-368
Sorting-264
Greedy-257
Depth-First Search-256
Database-215
Breadth-First Search-200
Tree-195
Binary Search-191
Matrix-176
Binary Tree-160
Two Pointers-151
Bit Manipulation-140
Stack-133
Heap (Priority Queue)-117
Design-116
Graph-108
Simulation-103
Prefix Sum-96
Backtracking-92
Counting-86
Sliding Window-73
Linked List-69
Union Find-66
Ordered Set-48
Monotonic Stack-47
Recursion-43
Trie-41
Binary Search Tree-40
Divide and Conquer-40
Enumeration-39
Bitmask-37
Queue-33
Memoization-32
Topological Sort-31
Geometry-30
Segment Tree-27
Game Theory-24
Hash Function-24
Binary Indexed Tree-21
Interactive-18
Data Stream-17
String Matching-17
Rolling Hash-17
Shortest Path-16
Number Theory-16
Combinatorics-15
Randomized-12
Monotonic Queue-9
Iterator-9
Merge Sort-9
Concurrency-9
Doubly-Linked List-8
Brainteaser-8
Probability and Statistics-7
Quickselect-7
Bucket Sort-6
Suffix Array-6
Minimum Spanning Tree-5
Counting Sort-5
Shell-4
Line Sweep-4
Reservoir Sampling-4
Eulerian Circuit-3
Radix Sort-3
Strongly Connected Componen-t2
Rejection Sampling-2
Biconnected Component-1
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