[환미니니] Week3 문제풀이

climbing-stairs/hwanmini.js

@@ -0,0 +1,18 @@
+// 시간복잡도 O(n)
+// 공간복잡도 O(n)
+
+/**
+ * @param {number} n
+ * @return {number}
+ */
+var climbStairs = function(n) {
+    const stairs = [1, 2]
+
+    for (let i = 2; i < n; i++) {
+        stairs[i] = stairs[i-1] + stairs[i-2]
+    }
+
+    return stairs[n-1]
+};
+
+console.log(climbStairs(5))

combination-sum/hwanmini.js

@@ -0,0 +1,32 @@
+// 시간복잡도: O(c^t)
+// 공간복잡도: O(t)
+
+/**
+ * @param {number[]} candidates
+ * @param {number} target
+ * @return {number[][]}
+ */
+var combinationSum = function(candidates, target) {
+    const result = [];
+
+    const dfs = (startIdx, subset = [], sum = 0) => {
+        if (sum > target) return;
+        if (sum === target) {
+            result.push([...subset]);
+            return;
+        }
+
+
+        for (let i = startIdx; i < candidates.length; i++) {
+            subset.push(candidates[i]);
+            dfs(i, subset, sum + candidates[i]);
+            subset.pop();
+        }
+    };
+
+    dfs(0);
+
+    return result;
+};
+
+console.log(combinationSum([2, 3, 6, 7], 7));

two-sum/hwanmini.js

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+// 시간복잡도 O(n log n)
+// 공간복잡도 O(n)
+
+/**
+ * @param {number[]} nums
+ * @param {number} target
+ * @return {number[]}
+ */
+var twoSum = function(nums, target) {
+
+
+    const numsArr = nums.map((num,idx) => [num,idx])
+    numsArr.sort((a,b) => a[0] - b[0])
+
+
+    let leftIdx = 0;
+    let rightIdx = nums.length - 1;
+
+    while (leftIdx <= rightIdx) {
+        if (numsArr[leftIdx][0] + numsArr[rightIdx][0] === target) {
+            return [numsArr[leftIdx][1], numsArr[rightIdx][1]]
+        }
+
+        if (numsArr[rightIdx][0] + numsArr[leftIdx][0] > target) {
+            rightIdx--
+        } else {
+            leftIdx++
+        }
+    }
+    return []
+};
+
+
+const nums = [2,7,11,15]
+const target = 9
+
+console.log(twoSum(nums,target))
+console.log(twoSum([3,2,4],6))
+console.log(twoSum([3,3],6))