Create _881.java (fishercoder1534#147)

* Create _881.java

* Update _881.java

please check once

* Add files via upload

* Delete 1961. Check If String Is a Prefix of Array.java

* Add files via upload

* 316 has difficulty level: Medium

Author: sushant-sinha

README.md

@@ -1034,7 +1034,7 @@ _If you like this project, please leave me a star._ ★
 | 319  |[Bulb Switcher](https://leetcode.com/problems/bulb-switcher/)| [Solution](../master/src/main/java/com/fishercoder/solutions/_319.java)                                                                  |                                                                               |Medium| Brainteaser
 | 318  |[Maximum Product of Word Lengths](https://leetcode.com/problems/maximum-product-of-word-lengths/)| [Solution](../master/src/main/java/com/fishercoder/solutions/_318.java)                                                                  |                                                                               |Medium| 
 | 317  |[Shortest Distance from All Buildings](https://leetcode.com/problems/shortest-distance-from-all-buildings/)| [Solution](../master/src/main/java/com/fishercoder/solutions/_317.java)                                                                  |                                                                               |Hard| 
-| 316  |[Remove Duplicate Letters](https://leetcode.com/problems/remove-duplicate-letters/)| [Solution](../master/src/main/java/com/fishercoder/solutions/_316.java)                                                                  |                                                                               |Hard| Stack, Recursion, Greedy
+| 316  |[Remove Duplicate Letters](https://leetcode.com/problems/remove-duplicate-letters/)| [Solution](../master/src/main/java/com/fishercoder/solutions/_316.java)                                                                  |                                                                               |Medium| Stack, Recursion, Greedy
 | 315  |[Count of Smaller Numbers After Self](https://leetcode.com/problems/count-of-smaller-numbers-after-self/)| [Solution](../master/src/main/java/com/fishercoder/solutions/_315.java)                                                                  |                                                                               |Hard| Tree
 | 314  |[Binary Tree Vertical Order Traversal](https://leetcode.com/problems/binary-tree-vertical-order-traversal/)| [Solution](../master/src/main/java/com/fishercoder/solutions/_314.java)                                                                  |                                                                               |Medium| HashMap, BFS
 | 313  |[Super Ugly Number](https://leetcode.com/problems/super-ugly-number/)| [Solution](../master/src/main/java/com/fishercoder/solutions/_313.java)                                                                  |                                                                               |Medium| 

src/main/java/com/fishercoder/solutions/1961. Check If String Is a Prefix of Array.java

@@ -0,0 +1,21 @@
+package com.fishercoder.solutions;
+
+public class _1961{
+    public class Solution1 {
+        public boolean isPrefixString(String s, String[] words) {
+
+            String t="";
+            int i=0;
+
+            while(t.length()<s.length() && i<words.length){
+                t+=words[i++];
+
+                if(t.equals(s))
+                    return true;
+            }
+
+            return false;
+
+        }
+    }
+}

src/main/java/com/fishercoder/solutions/_881.java

@@ -57,4 +57,28 @@ public int numRescueBoats(int[] people, int limit) {
             return boats;
         }
     }
+    
+    public static class Solution2 {
+        public int numRescueBoats(int[] people, int limit) {
+            Arrays.sort(people);
+            int end = people.length - 1;
+            int start = 0;
+            int boatcount = 0;
+            while (end >= start) {
+                if (people[end] == limit) {
+                    end--;
+                    boatcount++;
+                } else if (people[end] + people[start] <= limit) {
+                    start++;
+                    end--;
+                    boatcount++;
+                } else {
+                    end--;
+                    boatcount++;
+                }
+            }
+            return boatcount;
+        }
+    }
+  
 }