[1lsang] WEEK 03 solutions

combination-sum/1lsang.ts

@@ -0,0 +1,16 @@
+function combinationSum(candidates: number[], target: number): number[][] {
+  // arr: index까지 갈 수 있는 combinationSum
+  const arr:number[][][] = Array.from({ length: target + 1 }, () => [] as number[][]); 
+  // 0을 만들 수 있는 방법은 숫자가 없는 것
+  arr[0].push([] as number[]);
+
+  for (const candidate of candidates) {
+    for (let n = candidate; n <= target; n++) {
+      for (const combination of arr[n-candidate]) {
+        arr[n].push([...combination, candidate]);
+      }
+    }
+  }
+  console.log(arr);
+  return arr[target];
+};

number-of-1-bits/1lsang.ts

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+function hammingWeight(n: number): number {
+  // 최대 이진수 찾기
+  let s = 1;
+  while (s*2 <= n) {
+    s*=2;
+  }
+
+  // bit 세기
+  let cnt = 0;
+  while (n > 0) {
+    if (n - s >= 0) {
+      n -= s;
+      cnt++;
+    }
+    s /= 2;
+  }
+  return cnt;
+};

valid-palindrome/1lsang.ts

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+function isPalindrome(s: string): boolean {
+  // console.log('A'.charCodeAt(0), 'Z'.charCodeAt(0)); // 65 90
+  // console.log('a'.charCodeAt(0), 'z'.charCodeAt(0)); // 97 122
+  // console.log('0'.charCodeAt(0), '9'.charCodeAt(0)); // 48 57
+
+  // 문자열 변환 과정
+  let converted = ''
+  for (let c of s) {
+    const charCode = c.charCodeAt(0);
+    if (charCode >= 65 && charCode <= 90) {
+      converted += c.toLowerCase();
+    }
+    else if ((charCode >= 97 && charCode <= 122) || (charCode >= 48 && charCode <= 57)) {
+      converted += c;
+    }
+  }
+
+  // palindrome 판단 조건
+  const length = converted.length;
+
+  for (let i = 0; i < length/2; i ++) {
+    if (converted[i] !== converted[length - 1 - i]) return false;
+  }
+
+  return true;  
+};