code hunt 题解三 （java版）

02.01

public class Program {
public static int[] Puzzle(int n) {
int[] res = new int
;
for (int i = 0; i < n; i++) {
res[i] = i;
}
return res;
}
}

02.02
public class Program {
public static int[] Puzzle(int n) {
int[] res = new int
;
for (int i = 0; i < n; i++) {
res[i] = n*i;
}
return res;
}
}02.03
public class Program {
public static int[] Puzzle(int n) {
int[] res = new int
;
for (int i = 0; i < n; i++) {
res[i] = i*i;
}
return res;
}
}

02.04
public class Program {
public static int Puzzle(int[] v) {
int sum = 0;
for (int i = 0; i < v.length; i++) {
sum+=v[i];
}
return sum;
}
}02.05  求平方和
public class Program {
public static int Puzzle(int n) {
return n*(n-1)*(2*n-1)/6;
}
}02.06 求‘a’的个数
public class Program {
public static int Puzzle(String s) {
String s2 = s.replace("a","");
return s.length()-s2.length();
}
}02.07 求x的个数
public class Program {
public static int Puzzle(String s, char x) {
String s2 = s.replace(x+"","");
return s.length()-s2.length();
}
}