@skysbjdy
2016-12-24T06:38:05.000000Z
字数 5631
阅读 12673
Interview
ArraySum:
Bug: sum = arr[i]
Fixed: sum += arr[i]
Count Occurence: 统计某数在数组中出现的次数
Bug: while loop 里面 i++
Check Grade: 计算GPA
Bug: "||"
Fixed: "&&"
Remove Element: 删除数组特定位置的元素, 超出返回则返回原数组
Bug: arr[i++] 第五行
Fixed: arr[i + 1]
public static int[] removeElement(int arr[], int index) {int i, j, len = arr.length;if (index < len) {for (i = index; i < len - 1; i++) {arr[i] = arr[i+1];}int rarr[] = new int[len - 1];for (i = 0; i < len - 1; i++) {rarr[i] = arr[i];}} elsereturn arr;}
Digit Count: 返回num%len(num) == 0 or != 0
Bug: 最后返回时, num已经是0了. 所以之前要先保存起来.
public int find(int num) {int count = 0;int temp = num; //add a temporary variablewhile (num ! = 0) {num = num / 10;count++;}//return num % count; <--Bugreturn temp % count; //Fixed}
Sort Array
Bug: 大于小于符号写反
Fixed: arr[i] < arr[j]降序, arr[i] > arr[j]升序.
public static int[] sortArray(int[] arr) {int len = arr.length;int small, pos, i, j, temp; //small, pos can be deletedfor (i = 0; i <= len - 1; i++) {for (j = i; j < len; j++) {temp = 0;if (arr[i] < arr[j]) { // Bug '<' should be '>'temp = arr[i];arr[i] = arr[j];arr[j] = temp;}}}return arr;}
Sort Array 2
Bug: 大于小于符号写反
Fixed: arr[i] < arr[j]降序, arr[i] > arr[j]升序.
//这是一个正确的降序排列算法public static int[] sortArray2(int arr[]) {int i, max, location, j, temp, len = arr.length;for (i = 0; i < len; i++) {max = arr[i];location = i;for (j = i; j < len; j++) {if (max < arr[j]) {max = arr[j];location = j;}}temp = arr[i];arr[i] = arr[location];arr[location] = temp;}return arr;}
Replace values 数组长度是偶数就把元素都改成1, 奇数就都改成0
Bug: for loop里面 i <= len, j < = len
Fixed: i < len, j < len
public static int[] replaceValues(int arr[]) {int i, j, len = arr.length;if (len % 2 == 0) {for (i = 0; i < len; i++) { //fixedarr[i] = 0;}} else {for (j = 0; j < len; j++) { //fixedarr[j] = 1;}}return arr;}
Reverse array
但是class的名字居然是sort array
Bug: arr[len-1]改成 arr[len-i-1] for循环里 len +=1去掉
public static int[] reverseArray(int[] arr) {int i, temp, originalLen = arr.length;int len = originalLen;for (i = 0; i < originalLen / 2; i++) {temp = arr[len - i - 1];arr[len - i - 1] = arr[i]; //fixedarr[i] = temp;// len +=1;}return arr;}
Even Odd pattern
Bug: for 循环缺大括号
public static void print4(int num) {int i, print = 0;if (num % 2 == 0) {print = 0;for (i = 0; i < num; i++) {System.out.print(print + " ");print += 2;}} else {print = 1;for (i = 0; i < num; i++) {System.out.print(print + " ");print += 2;}}}
Manchester Code: 假设第一个element前面的数字是0
Bug: 把判断语句的 == 改成 != (考虑i == 0的情况)
Selection sort
Bug: if里面的判断 arr[min] > arr[x], 改成arr[min] > arr[y]
// selection sort in ascending orderfor (x = 0; x < n; x++) {int index_of_min = x;for (y = x; y < n; y++) {//if (arr[index_of_min] > arr[x]) { // Bugif (arr[index_of_min] > arr[y])y = index_of_min;}int temp = arr[x];arr[x] = arr[index_of_min];arr[index_of_min] = temp;}}// bubble sort in descending orderfor (int x = 0; x < n; x++) {for (int y = x; y < n; y++) {if (arr[x] < arr[y]) {int temp = arr[x];arr[x] = arr[y];arr[y] = temp;}}}
Insertion sort
Bug: 大于小于x
for (int i = 1; i < n; i++) {if (arr[i - 1] > arr[i]) { int temp = arr[i]; //Bugint j = i;while (j > 0 && arr[j - 1] > temp) { //Bug arr[j - 1] > temparr[j] = arr[j - 1];j--;}arr[j] = temp;}}
Print Pattern
a
ab
abc
Bug: char ch = 'a' 定义在了for loop前面, 移进来就好, 同时删除了没用的变量
//This code is correctpublic static void print2(int row) {for (int i = 1; i <= row; i++) {char ch = 'a';char print = ch;for (int j = 1; j <= i; j++) {System.out.print((print++));}System.out.println();}}//可以继续优化:public static void print2(int row) {for (int i = 1; i <= row; i++) {char ch = 'a';for (int j = 1; j <= i; j++) {System.out.print((ch++));}System.out.println();}}
Print Pattern
Row number = 3
11
1111
111111
Row number = 2
11
1111
Bug: 第一层for循环少了大括号,
public static void print3(int row) {int x = 1;for (int i = 1; i <= row; i++) { //添加括号for (int j = i; j > 0; j--) {System.out.print(x + "" + x);}System.out.println();} //添加括号}
remove duplicates from unsorted array
Bug: 循环下标要从i + 1开始