add 1653 & 3760

Author: clingoram

javascript/LeetCode/String/1653.js

@@ -0,0 +1,47 @@
+/**
+ * 1653. Minimum Deletions to Make String Balanced
+ * 
+ * 參數s中只有'a' & 'b'這兩個字母。
+ * 刪除任一字母使s balanced，若不存在一對index (i,j) 使得 i < j 且 s[i] = 'b' 且 s[j] = 'a'，則s 是balanced。
+ * 回傳至少須刪除幾次(操作幾次)才能使s balanced
+ * 
+ * 
+ * @param {string} s
+ * @return {number}
+ */
+var minimumDeletions = function(s) {
+  // balanced string中，b不能出現在a之後
+  // no such 'b' at s[i] where s[j] is 'a' and i < j
+
+    // TC:O(N)
+    // 計算a,b各自出現幾次
+    let countA = 0,countB = 0;
+    let minDel = s.length;
+    // 先計算a出現幾次
+    for(let i = 0;i < s.length;++i) {
+      if(s[i] === "a"){
+        countA++;
+      }
+    }
+    // 之後再次迴圈，若遇到a則--
+    for(let i = 0; i < s.length;++i) {
+      if(s[i] === "a"){
+        countA--;
+      }
+      // 不斷更新比較雙方次數
+      minDel = Math.min(minDel,countA + countB);
+
+      // 遇到b，++
+      if(s[i] === "b"){
+        countB++;
+      }
+    }
+    return minDel;
+};
+let s = "aababbab";
+/*Output: 2
+Explanation: You can either:
+Delete the characters at 0-indexed positions 2 and 6 ("aababbab" -> "aaabbb"), or
+Delete the characters at 0-indexed positions 3 and 6 ("aababbab" -> "aabbbb").
+*/
+console.log(minimumDeletions(s));

javascript/LeetCode/String/3760.js

@@ -0,0 +1,31 @@
+/**
+ * 3760. Maximum Substrings With Distinct Start
+ * Difficulty:Medium
+ * 
+ * @param {string} s
+ * @return {number}
+ */
+var maxDistinct = function(s) {
+    // 計算字串中，若每個開頭是跟另一substring開頭不同的字母，可以有幾種組合
+    // 計算每個字母出現次數
+
+    // let map = new Map();
+    // for(let i = 0; i < s.length;++i) {
+    //   map = map.has(s[i]) ? map.set(s[i], map.get(s[i]) + 1) : map.set(s[i], 1);
+    // }
+    // return map.size;
+
+    // solution 2.
+    /**
+     * TC: O(N) => 
+     * 將s弄成陣列，須loop所有元素，因此O(N)
+     * new Set(...) 將每個元素插入set，add是O(1)但要做n次，因此O(N)
+     * size 讀取長度，因此O(1)
+     * 
+     * new Set([...s]) 需要loop並插入所有元素，所以整體是O(n)
+     * */
+    return new Set([...s]).size;
+};
+let s = "abab";
+// 2
+console.log(maxDistinct(s))

javascript/index.js

@@ -1,9 +1,7 @@
 // debugger
-import { format } from 'node:path';
 import {ExecutionTimer} from './time.js';
 import assert from 'node:assert/strict';
 import { count } from 'node:console';
-import { lchown } from 'node:fs';
 
 /*
 22. Generate Parentheses
@@ -1260,25 +1258,3 @@ var minRemoval = function(nums, k) {
 // console.log(minRemoval(nums,k));
 
 
-/**
- * 1653. Minimum Deletions to Make String Balanced
- * 
- * 參數s中只有'a' & 'b'這兩個字母。
- * 刪除任一字母使s balanced，若不存在一對index (i,j) 使得 i < j 且 s[i] = 'b' 且 s[j] = 'a'，則s 是balanced。
- * 回傳最小須刪除幾次才能使s balanced
- * 
- * 
- * @param {string} s
- * @return {number}
- */
-var minimumDeletions = function(s) {
-    
-};
-// let s = "aababbab";
-/*Output: 2
-Explanation: You can either:
-Delete the characters at 0-indexed positions 2 and 6 ("aababbab" -> "aaabbb"), or
-Delete the characters at 0-indexed positions 3 and 6 ("aababbab" -> "aabbbb").
-*/
-// console.log(minimumDeletions(s));
-