update

Author: Cocoolanu

CodingBat/Warmup-1/backAround.java

@@ -0,0 +1,12 @@
+/*
+Given a string, take the last char and return a new string with the last char added at the front and back, so "cat" yields "tcatt". The original string will be length 1 or more.
+eg：
+backAround("cat") → "tcatt"
+backAround("Hello") → "oHelloo"
+backAround("a") → "aaa"
+*/
+
+public String backAround(String str) {
+  String lastChr = str.substring(str.length()-1);
+  return lastChr + str + lastChr; 
+}

CodingBat/Warmup-1/close10.java

@@ -0,0 +1,20 @@
+/*
+Given 2 int values, return whichever value is nearest to the value 10, or return 0 in the event of a tie. Note that Math.abs(n) returns the absolute value of a number.
+eg:
+close10(8, 13) → 8
+close10(13, 8) → 8
+close10(13, 7) → 0
+*/
+
+public int close10(int a, int b) {
+  int aDiff = Math.abs(a-10);
+  int bDiff = Math.abs(b-10);
+  
+  if(aDiff == bDiff){
+    return 0;
+  }else if(aDiff > bDiff){
+    return b;
+  }else{
+    return a; 
+  }
+}

CodingBat/Warmup-1/delDel.java

@@ -0,0 +1,15 @@
+/*
+Given a string, if the string "del" appears starting at index 1, return a string where that "del" has been deleted. Otherwise, return the string unchanged.
+eg:
+delDel("adelbc") → "abc"
+delDel("adelHello") → "aHello"
+delDel("adedbc") → "adedbc"
+*/
+
+public String delDel(String str) {
+  if(str.length()>3 && str.substring(1,4).equals("del")){
+    return str.substring(0,1) + str.substring(4);
+  }else{
+    return str; 
+  }
+}

CodingBat/Warmup-1/endUp.java

@@ -0,0 +1,16 @@
+/*
+Given a string, return a new string where the last 3 chars are now in upper case. If the string has less than 3 chars, uppercase whatever is there. Note that str.toUpperCase() returns the uppercase version of a string.
+eg:
+endUp("Hello") → "HeLLO"
+endUp("hi there") → "hi thERE"
+endUp("hi") → "HI"
+*/
+
+public String endUp(String str) {
+  if(str.length()<3){
+    return str.toUpperCase();
+  }  
+  else{
+    return str.substring(0, str.length()-3) + str.substring(str.length()-3).toUpperCase(); 
+  }
+}

CodingBat/Warmup-1/everyNth.java

@@ -0,0 +1,16 @@
+/*
+Given a non-empty string and an int N, return the string made starting with char 0, and then every Nth char of the string. So if N is 3, use char 0, 3, 6, ... and so on. N is 1 or more.
+eg:
+everyNth("Miracle", 2) → "Mrce"
+everyNth("abcdefg", 2) → "aceg"
+everyNth("abcdefg", 3) → "adg"
+*/ 
+
+public String everyNth(String str, int n) {
+  String result = ""; 
+  
+  for(int i=0; i< str.length(); i+=n){
+    result += str.charAt(i);
+  }
+  return result; 
+}

CodingBat/Warmup-1/front22.java

@@ -0,0 +1,17 @@
+/*
+Given a string, take the first 2 chars and return the string with the 2 chars added at both the front and back, so "kitten" yields"kikittenki". If the string length is less than 2, use whatever chars are there.
+eg:
+front22("kitten") → "kikittenki"
+front22("Ha") → "HaHaHa"
+front22("abc") → "ababcab"
+*/
+
+public String front22(String str) {
+  String front; 
+  if (str.length() < 2){
+    front = str;  
+  }else{
+    front = str.substring(0,2);
+  }
+  return front + str + front; 
+}

CodingBat/Warmup-1/front3.java

@@ -0,0 +1,19 @@
+/*
+
+Given a string, we'll say that the front is the first 3 chars of the string. If the string length is less than 3, the front is whatever is there. Return a new string which is 3 copies of the front.
+eg:
+front3("Java") → "JavJavJav"
+front3("Chocolate") → "ChoChoCho"
+front3("abc") → "abcabcabc"
+*/
+
+public String front3(String str) {
+  String front; 
+  if(str.length() < 3){
+    front = str;
+  }else{
+    front = str.substring(0,3);
+  }
+  
+  return front + front + front; 
+}

CodingBat/Warmup-1/frontBack.java

@@ -0,0 +1,15 @@
+/*
+Given a string, return a new string where the first and last chars have been exchanged.
+eg:
+frontBack("code") → "eodc"
+frontBack("a") → "a"
+frontBack("ab") → "ba"
+*/
+
+public String frontBack(String str) {
+  if (str.length() <= 1){
+    return str;
+  }else{
+    return str.charAt(str.length()-1) + str.substring(1,str.length()-1) + str.charAt(0);
+  }
+}

CodingBat/Warmup-1/hasTeen.java

@@ -0,0 +1,13 @@
+/*
+We'll say that a number is "teen" if it is in the range 13..19 inclusive. Given 3 int values, return true if 1 or more of them are teen.
+eg:
+hasTeen(13, 20, 10) → true
+hasTeen(20, 19, 10) → true
+hasTeen(20, 10, 13) → true
+*/
+
+public boolean hasTeen(int a, int b, int c) {
+  return (a>=13 && a<=19) ||
+         (b>=13 && b<=19) ||
+         (c>=13 && c<=19);
+}

CodingBat/Warmup-1/icyHot.java

@@ -0,0 +1,11 @@
+/*
+Given two temperatures, return true if one is less than 0 and the other is greater than 100.
+eg:
+icyHot(120, -1) → true
+icyHot(-1, 120) → true
+icyHot(2, 120) → false
+*/
+
+public boolean icyHot(int temp1, int temp2) {
+  return (temp1<0 && temp2>100) || (temp2<0 && temp1>100);
+}