[jun0811] WEEK 03 solutions

combination-sum/jun0811.js

@@ -0,0 +1,27 @@
+/**
+ * @param {number[]} candidates
+ * @param {number} target
+ * @return {number[][]}
+ */
+var combinationSum = function (candidates, target) {
+  const result = [];
+  candidates.sort((a, b) => a - b);
+  function backTracking(start, arr, total) {
+    if (total == target) {
+      result.push([...arr]);
+      return;
+    }
+
+    for (let i = start; i < candidates.length; i++) {
+      const cur = candidates[i];
+      if (cur + total > target) {
+        return;
+      }
+
+      backTracking(i, [...arr, cur], total + cur);
+    }
+  }
+
+  backTracking(0, [], 0);
+  return result;
+};

decode-ways/jun0811.js

@@ -0,0 +1,32 @@
+/**
+ * @param {string} s
+ * @return {number}
+ */
+
+function check(str) {
+  if (str.length == 2) {
+    if (str[0] == '0') return false;
+  }
+  if (str >= 1 && str <= 26) return true;
+  return false;
+}
+
+var numDecodings = function (s) {
+  if (s[0] == '0') return 0;
+  const dp = [1, 1];
+
+  for (let i = 2; i <= s.length; i++) {
+    let tmp = dp[i - 1] + dp[i - 2];
+
+    // 2글자 체크 -> dp[i-2]을 뺴줌
+    const two_c = String(s[i - 2]) + String(s[i - 1]);
+    if (!check(two_c)) tmp -= dp[i - 2];
+
+    // 1글자 체크 -> dp[i-1]을 빼줌
+    if (!check(s[i - 1])) tmp -= dp[i - 1];
+
+    if (tmp == 0) return 0;
+    dp[i] = tmp;
+  }
+  return dp[s.length];
+};

maximum-subarray/jun0811.js

@@ -0,0 +1,15 @@
+/**
+ * @param {number[]} nums
+ * @return {number}
+ */
+var maxSubArray = function (nums) {
+  const dp = [nums[0]];
+  for (let i = 1; i < nums.length; i++) {
+    const cur = nums[i];
+    if (dp[i - 1] < 0) dp[i] = cur;
+    else {
+      dp[i] = dp[i - 1] + cur;
+    }
+  }
+  return Math.max(...dp);
+};

number-of-1-bits/jun0811.js

@@ -2,6 +2,9 @@
  * @param {number} n
  * @return {number}
  */
+
+// 1주차에 풀이 후 제출..
+
 var hammingWeight = function (n) {
   let res = 0;
   while (n > 0) {

valid-palindrome/jun0811.js

@@ -0,0 +1,32 @@
+var isPalindrome = function (s) {
+  let left = 0;
+  let right = s.length - 1;
+
+  while (left < right) {
+    while (left < right && !isAlphaNumeric(s[left])) {
+      left++;
+    }
+
+    while (left < right && !isAlphaNumeric(s[right])) {
+      right--;
+    }
+
+    if (s[left].toLowerCase() !== s[right].toLowerCase()) {
+      return false;
+    }
+
+    left++;
+    right--;
+  }
+
+  return true;
+};
+
+function isAlphaNumeric(char) {
+  const code = char.charCodeAt(0);
+  return (
+    (code >= 48 && code <= 57) || // 0-9
+    (code >= 65 && code <= 90) || // A-Z
+    (code >= 97 && code <= 122)
+  ); // a-z
+}