(LeetCode) Remove duplicate letters

LeetCode/removeDuplicateLetters.js

@@ -0,0 +1,68 @@
+/*
+Given a string s, remove duplicate letters so that every letter appears once and only once. You must make sure your result is the smallest in lexicographical order among all possible results.
+
+Note: This question is the same as 1081: https://leetcode.com/problems/smallest-subsequence-of-distinct-characters/
+
+
+
+Example 1:
+
+Input: s = "bcabc"
+Output: "abc"
+Example 2:
+
+Input: s = "cbacdcbc"
+Output: "acdb"
+
+
+Constraints:
+
+1 <= s.length <= 104
+s consists of lowercase English letters.
+ */
+/**
+ * @param {string} s
+ * @return {string}
+ */
+var removeDuplicateLetters = function(s) {
+    const counts = {};
+    const stack = [];
+    const seen = new Set();
+
+    for (let i = 0; i < s.length; i++) {
+        counts[s[i]] = counts[s[i]] + 1 || 1;
+    }
+    // b c a b c
+    // scan letters
+    // for each letter existing in the stack, if there are remaining counts for it, and it is greater than current, pop
+    // keep track of seen to prevent adding later dupes
+    for (let i = 0; i < s.length; i++) {
+        counts[s[i]]--;
+        // do not add this dupe
+        if (seen.has(s[i])) {
+            continue;
+        }
+        while (stack.length && stack[stack.length-1] > s[i] && counts[stack[stack.length-1]] > 0) {
+            const c = stack.pop();
+            // unmark
+            seen.delete(c);
+        }
+        stack.push(s[i]);
+        seen.add(s[i]);
+    }
+
+    return stack.join('');
+};
+
+/*
+b c a b c a
+{
+a: 0
+b: 0
+c: 0
+}
+
+{ a b }
+
+[ a c ]
+ */

LeetCode/wordSearch.js

@@ -0,0 +1,52 @@
+/**
+ * @param {character[][]} board
+ * @param {string} word
+ * @return {boolean}
+ */
+var exist = function(board, word) {
+    const rows = board.length;
+    const cols = board[0].length;
+
+    let cur = 0;
+    for (let i = 0; i < rows; i++) {
+        for (let j = 0; j < cols; j++) {
+            if (board[i][j] === word[0]) {
+                if (search(i, j, 0)) {
+                    return true;
+                }
+            }
+
+        }
+    }
+
+    return false;
+
+    function search(i, j, c, visited = new Set()) {
+        if (i < 0 || i === rows || j < 0 || j === cols || visited.has(`${i}-${j}`)) {
+            return false;
+        }
+        // console.log(i, j, board[i][j], word[c], visited)
+        if (c === word.length - 1 && board[i][j] === word[c]) {
+            return true;
+        }
+        let found = true;
+
+        visited.add(`${i}-${j}`);
+        found = found && board[i][j] === word[c] && (
+            search(i-1, j, c+1, visited) ||
+            search(i, j-1, c+1, visited) ||
+            search(i+1, j, c+1, visited) ||
+            search(i, j+1, c+1, visited)
+        );
+        visited.delete(`${i}-${j}`);
+
+        return found;
+    }
+};
+
+console.log(
+    exist(
+        [["A","B","C","E"],["S","F","C","S"],["A","D","E","E"]],
+    "ABCCED"
+    )
+);