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LeetCode May 2020
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// LeetCode May 2020 |
Author
wovalle
commented
May 22, 2020
•
// 21.js
/**
* @param {number[][]} matrix
* @return {number}
*/
const isValidSubMatrix = (matrix, x, y, side) => {
if (y + side > matrix.length || x + side > matrix[y].length) {
return false;
}
if (side === 1) {
return matrix[y][x] === 1;
}
for (let sy = y; sy < y + side; sy++) {
for (let sx = x; sx < x + side; sx++) {
if (!matrix[sy][sx]) {
return false;
}
}
}
return true;
};
var countSquares = function (matrix) {
const times = Math.min(matrix.length, matrix[0].length);
let number = 0;
for (let side = 1; side <= times; side++) {
for (let y = 0; y < matrix.length; y++) {
for (let x = 0; x < matrix[y].length; x++) {
if (isValidSubMatrix(matrix, x, y, side)) {
number++;
}
}
}
}
return number;
};
// Time: O(n ^ 3) or O(n ^ 4), lol
// Space: O(1)
// 22.js
/**
* @param {string} s
* @return {string}
*/
var frequencySort = function(s) {
// It would be nice if we had some type of ordered Map
// to prevent the sort in line 15
const freq = {}
for (let letter of s) {
freq[letter] = (freq[letter] || 0) + 1
}
return Object.entries(freq)
.sort((a, b) => b[1] - a[1])
.map(e => e[0].repeat(e[1]))
.join('')
};
// Time: O(n)
// Space: O(n)
// 23.js
/**
* @param {number[][]} A
* @param {number[][]} B
* @return {number[][]}
*/
var intervalIntersection = function(A, B) {
const getIntersection = (a, b) => {
if (a[1] < b[0] || a[0] > b[1])
return null
return [Math.max(a[0], b[0]), Math.min(a[1], b[1])]
}
let pivotA = 0
let pivotB = 0
const answer = []
while (pivotA < A.length && pivotB < B.length) {
const intersection = getIntersection(A[pivotA], B[pivotB])
if(intersection) {
answer.push(intersection)
}
if(A[pivotA][1] < B[pivotB][1]) {
pivotA++
} else {
pivotB++
}
}
return answer
};
// Time: O(A + B) = O(n)
// Space: O(N)
// 24.js
const getLast = (arr, level = 1) => (arr.length ? arr[arr.length - level] : null);
const bstFromPreorder = function (preorder) {
if (!preorder.length) {
return null;
}
const leaves = [[new TreeNode(preorder.shift()), -Infinity, Infinity]];
while (preorder.length) {
const currentVal = preorder.shift();
while (currentVal > getLast(leaves)[2] || currentVal < getLast(leaves)[1]) {
leaves.pop();
}
const [leave, min, max] = getLast(leaves);
if (currentVal > leave.val) {
leave.right = new TreeNode(currentVal);
leaves.push([leave.right, leave.val, max]);
} else if (currentVal < leave.val) {
leave.left = new TreeNode(currentVal);
leaves.push([leave.left, min, leave.val]);
}
}
return leaves[0][0];
};
// Time: O(n)
// Space: O(n)
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