[서인] 10-1. 계단오르기

08. 재귀함수와 완전탐색(DFS;깊이우선탐색)/14. 조합 구하기/이서인/index.js

@@ -1,7 +1,20 @@
 function solution(n, m) {
-  let answer = [];
+  let elements = []
+
+  function DFS(el, part = "") {
+    if (part.length === m) {
+      elements.push(part);
+      return;
+    }
+    if (el > n) return;
+
+    DFS(el + 1, part + el)
+    DFS(el + 1, part);
+  }
+
+  DFS(1);
 
-  return answer;
+  return [...elements, elements.length].join("\n")
 }
 
 console.log(solution(4, 2));

08. 재귀함수와 완전탐색(DFS;깊이우선탐색)/15. 수들의 조합/이서인/index.js

@@ -1,8 +1,23 @@
 function solution(n, k, arr, m) {
-  let answer = 0;
+  let parts = [];
 
-  return answer;
+  function DFS(index, part = [], count = 0) {
+    if (count === k) {
+      parts.push(part.slice());
+      return;
+    }
+    if (index >= n) return;
+
+    DFS(index + 1, part.concat(arr[index]), count + 1);
+    DFS(index + 1, part, count);
+  }
+
+  DFS(0,[])
+
+  return parts.filter(el => el.reduce((a, b) => a + b, 0) % m === 0).length
 }
 
 let arr = [2, 4, 5, 8, 12];
 console.log(solution(5, 3, arr, 6));
+
+

09. 그래프와 탐색(DFS, BFS;너비우선탐색)/02. 경로탐색(DFS)/이서인/index.js

@@ -1,5 +1,29 @@
 function solution(n, arr) {
   let answer = 0;
+  const graph = Array.from({ length: n + 1 }, () => new Array(n + 1).fill(0));
+  const visited = new Array(n + 1).fill(false);
+
+  for (const [s, e] of arr) {
+    graph[s][e] = 1;
+  }
+
+  function DFS(v) {
+    if (v === n) {
+      answer++;
+      return;
+    }
+
+    for (let i = 1; i <= n; i++) {
+      if (graph[v][i] === 1 && !visited[i]) {
+        visited[i] = true;
+        DFS(i);
+        visited[i] = false;
+      }
+    }
+  }
+
+  visited[1] = true;
+  DFS(1);
 
   return answer;
 }

09. 그래프와 탐색(DFS, BFS;너비우선탐색)/03. 경로탐색(인접리스트)/이서인/index.js

@@ -1,6 +1,31 @@
 function solution(n, arr) {
   let answer = 0;
+  const graph = Array.from({length: n + 1}, () => [])
+  const visited = new Array(n + 1).fill(false)
 
+  for (const [s, e] of arr) {
+    graph[s].push(e)
+  }
+
+  function DFS(v) {
+    if (v === n) {
+      answer++
+      return
+    }
+
+      visited[v] = true;
+
+      for (const next of graph[v]) {
+        if (!visited[next]) {
+          DFS(next)
+        }
+      }
+
+    visited[v] = false
+  }
+
+  DFS(1) 
+
   return answer;
 }
 

09. 그래프와 탐색(DFS, BFS;너비우선탐색)/04. 미로탐색/이서인/index.js

@@ -1,9 +1,65 @@
 function solution(board) {
   let answer = 0;
+  const n = board.length;
+  const visited = Array.from({ length: n }, () => Array(n).fill(false));
 
+  function DFS(x, y) {
+    if (x === n - 1 && y === n - 1) {
+      answer++;
+      return;
+    }
+
+    visited[x][y] = true;
+
+    const directions = [
+      [-1, 0],
+      [1, 0],
+      [0, -1],
+      [0, 1]
+    ];
+
+    for (const [dx, dy] of directions) {
+      const nx = x + dx;
+      const ny = y + dy;
+
+      if (nx >= 0 && nx < n && ny >= 0 && ny < n && !visited[nx][ny] && board[nx][ny] === 0) {
+        DFS(nx, ny);
+      }
+    }
+
+    visited[x][y] = false;
+  }
+    if (board[0][0] === 0) {
+      DFS(0, 0)
+    }
+
   return answer;
 }
 
+// 틀린 풀이 => visited 배열을 1차원으로 설정했다.
+// function solution(board) {
+//   let answer = 0;
+//   const visited = new Array(board.length).fill(false);
+
+//   function DFS(v) {
+//     if (v === board.length - 1) {
+//       answer++;
+//       return;
+//     }
+//     for (let i = 1; i <= board.length - 1; i++) {
+//       if (board[v][i] === 0 && !visited[i]) {
+//         visited[i] = true
+//         DFS(i)
+//         visited[i] = false
+//       }
+//     }  
+//   }
+//   visited[1] = true;
+//   DFS(1)
+
+//   return answer;
+// }
+
 let arr = [
   [0, 0, 0, 0, 0, 0, 0],
   [0, 1, 1, 1, 1, 1, 0],

09. 그래프와 탐색(DFS, BFS;너비우선탐색)/05. 이진트리 넓이우선탐색(BFS)/이서인/index.js

@@ -1,7 +1,17 @@
 function solution() {
-  let answer = '';
-
-  return answer;
-}
+    const queue = [];
+    let answer = ''
+    queue.push(1)
 
+  while (queue.length) {
+    console.log(queue);
+      let v = queue.shift()
+    answer += v + "";
+    for (let newv of [v * 2, v * 2 + 1]) {
+      if (newv > 7) continue;
+      queue.push(newv)
+    }
+  }
+  return answer
+  }
 console.log(solution());

09. 그래프와 탐색(DFS, BFS;너비우선탐색)/06. 송아지 찾기(BFS)/이서인/index.js

@@ -1,7 +1,23 @@
 function solution(s, e) {
-  let answer = 0;
+  const directions = [1, -1, 5];
+  const visited = new Array(10001).fill(false);
+  const queue = [];
 
-  return answer;
+  queue.push([s, 0]);
+  visited[s] = true;
+
+  while (queue.length) {
+    const [current, jumps] = queue.shift();
+    if (current === e) return jumps;
+
+    for (let direction of directions) {
+      const next = current + direction;
+      if (next >= 0 && next <= 10000 && !visited[next]) {
+        visited[next] = true;
+        queue.push([next, jumps + 1]);
+      }
+    }
+  }
 }
 
-console.log(solution(8, 3));
+console.log(solution(5, 14));

09. 그래프와 탐색(DFS, BFS;너비우선탐색)/07. 섬나라 아일랜드(BFS)/이서인/index.js

@@ -1,5 +1,40 @@
 function solution(board) {
   let answer = 0;
+  const n = board.length;
+
+  const directions = [
+    [-1, 0],
+    [1, 0],
+    [0, -1],
+    [0, 1],
+    [-1, -1],
+    [-1, 1],
+    [1, -1],
+    [1, 1]
+  ];
+
+  function DFS(x, y) {
+
+    board[x][y] = 0;
+
+    for (const [dx, dy] of directions) {
+      const nx = x + dx;
+      const ny = y + dy;
+
+      if (nx >= 0 && nx < n && ny >= 0 && ny < n && !visited[nx][ny] && board[nx][ny] === 1) {
+        DFS(nx, ny);
+      }
+    }
+  }
+
+  for (let i = 0; i < n; i++) {
+    for (let j = 0; j < n; j++) {
+      if (board[i][j] === 1) {
+        answer++;
+        DFS(i, j);
+      }
+    }
+  }
 
   return answer;
 }

09. 그래프와 탐색(DFS, BFS;너비우선탐색)/07. 섬나라 아일랜드(DFS)/이서인/index.js

@@ -1,5 +1,44 @@
 function solution(board) {
   let answer = 0;
+  const n = board.length;
+
+  const directions = [
+  [-1, 0],
+  [1, 0],
+  [0, -1],
+  [0, 1],
+  [-1, -1],
+  [-1, 1],
+  [1, -1],
+  [1, 1]]
+
+  function BFS(x, y) {
+    let queue = [[x, y]];
+    board[x][y] = 0;
+
+    while (queue.length) {
+      let [cx, cy] = queue.shift();
+
+      for (const [dx, dy] of directions) {
+        const nx = cx + dx;
+        const ny = cy + dy;
+
+        if (nx >= 0 && nx < n && ny >= 0 && ny < n && board[nx][ny] === 1) {
+          board[nx][ny] = 0;
+          queue.push([nx, ny]);
+        }
+      }
+    }
+  }
+
+  for (let i = 0; i < n; i++) {
+    for (let j = 0; j < n; j++) {
+      if (board[i][j] === 1) {
+        answer++;
+        BFS(i, j)
+      }
+    }
+  }
 
   return answer;
 }

10. Dynamic programming(동적계획법)/01. 계단오르기/이서인/index.js

@@ -1,7 +1,15 @@
 function solution(n) {
-  let answer = 0;
+  if (n === 1) return 1;
+  if (n === 2) return 2;
 
-  return answer;
+  let dp = new Array(n + 1).fill(0);
+  dp[1] = 1;
+  dp[2] = 2;
+
+  for (let i = 3; i <= n; i++) {
+    dp[i] = dp[i - 1] + dp[i - 2];
+  }
+  return dp[n]
 }
 
 console.log(solution(7));