Added java solution for 14, 55 / python solution for 2420

java/055_Jump_Game.java

@@ -0,0 +1,49 @@
+import java.util.*;
+
+class Solution {
+    public boolean canJump(int[] nums) {
+        /*
+         * Constraints
+         * 1 <= nums.length <= 10^4
+         * 0 <= nums[i] <= 10^5
+         * 
+         * Solution
+         * 1. Use BFS Algorithm.
+         *   - reason 1 : have to ignore array which is not visited.
+         *   - reason 2 : we have to visit all possible array from array[start].
+         */
+
+        int N = nums.length;
+        ArrayDeque<Integer> q = new ArrayDeque<>();
+        boolean[] visited = new boolean[N];
+
+        // First, add first array index.
+        // And, set visited[first_index] to true.
+        q.add(0);
+        visited[0] = true;
+
+        // Axiom : if N is 1, result is true.
+        if(N == 1) return true;
+
+        // BFS algorithm
+        while(!q.isEmpty()) {
+            int cur = q.poll();
+
+            // find cur + 1 to cur + nums[cur]
+            for(int i = 1; i <= nums[cur]; i++) {
+                if(cur + i >= N - 1) return true;
+                int next = Math.min(cur + i, N - 1);
+
+                // set visited[next] to true and add index into queue.
+                // because of time limit(No overlap steps.)
+                if(!visited[next]) {
+                    visited[next] = true;
+                    q.add(next);
+                }
+            }
+        }
+
+        return false;
+
+    }
+}