java面试的算法题_java面试 - 经典算法题
题目一：
public class testClockwiseOutput { //顺时针打印一个矩阵 @Test public void test(){ int[][] num = new int[100][100]; int n = 4; int count =1; for(int i=0;i
num[i][j]=count++;
}
}
output(num,0,n-1);
} public void output(int[][] num,int start,int end){ if(start>=end || end<=0)return; for(int i=start;i<=end;i++){
System.out.println(num[start][i]);
} for(int i=start+1;i<=end;i++){
System.out.println(num[i][end]);
} for(int i=end-1;i>=start;i--){
System.out.println(num[end][i]);
} for(int i=end-1;i>start;i--){
System.out.println(num[i][start]);
}
output(num,start+1,end-1);
}
}
题目二：
给出一个排序好的数组和一个数，求数组中连续元素的和等于所给数的子数组
//给出一个排序好的数组和一个数，求数组中连续元素的和等于所给数的子数组 @Test public void test(){ int[] num = {1,2,2,3,4,5,6,7,8,9}; int sum = 7;
findSum(num,sum);
} public void findSum(int[] num,int sum){ int left=0; int right=0; for(int i=0;i
left = i;
right = i; while(curSum
curSum += num[right++];
} if(curSum==sum){ for(int j=left;j
System.out.print(num[j]+" ");
}
System.out.println();
}
}
}
题目三：
//字符数组组成的所有字符串 @Test public void test(){ //char[] cs = {'a','b','c','d','e'}; char[] cs = {'a','b','c'}; int length = cs.length;
recursionSwap(cs,0,length);
} public void swap(char[] cs,int index1,int index2){ char temp = cs[index1];
cs[index1]=cs[index2];
cs[index2]=temp;
} public void recursionSwap(char[] cs,int start,int length){ if(start>=length-1){
print(cs); return;
} for(int i=start;i
swap(cs,start,i);
recursionSwap(cs,start+1,length);
swap(cs,start,i);
}
} public void print(char[] cs){ for(int i=0;i
System.out.print(cs[i]);
}
System.out.println();
}
题目四：
//数组组成的最小数 @Test public void test(){ int[] num={1,5,9,13,442,44,6,21,211};
qsort(num,0,num.length-1);
System.out.println(Arrays.toString(num));
} public void qsort(int[] num,int left,int right){ if(left
qsort(num,left,partition-1);
qsort(num,partition+1,right);
}
} public int partition(int[] num,int left,int right){ int partition = num[left]; while(left
right--;
}
swap(num,left,right); while((num[left]==partition || isMBigerThanN(num,partition,num[left])) && left
left++;
}
swap(num,left,right);
} return left;
} public void swap(int[] num,int m,int n){ int temp = num[m];
num[m]=num[n];
num[n]=temp;
} public boolean isMBigerThanN(int[] num,int m,int n){
String num1 = String.valueOf(m);
String num2 = String.valueOf(n); int temp1 = Integer.parseInt(num1+num2); int temp2 = Integer.parseInt(num2+num1); if(temp1>temp2){ return true;
} else{ return false;
}
}
题目五：
//子数组最大和 @Test public void test(){ int[] num = {1,-2,3,10,-4,7,2,-5}; //int[] num = {1,-2,3,10,-4,10,2,-5}; System.out.println(maxSum(num));
} public int maxSum(int[] num){ int curSum = 0; int curMaxSum = -99999999; int start = 0; int end = 0; for(int i=0;i
curSum = num[i];
start = i;
} else{
curSum += num[i];
} if(curSum>curMaxSum){
curMaxSum = curSum;
end = i;
}
} for(int i = start;i<=end;i++){
System.out.println(num[i]);
} return curMaxSum;
}
题目六：
public class testMinStack { //自定义栈，min函数得到当前最小值 @Test public void test(){
MinStack ms = new MinStack();
ms.push(5);
System.out.println(ms.min());
ms.push(6);
ms.push(2);
ms.push(1);
System.out.println(ms.min());
ms.pop();
System.out.println(ms.min());
ms.pop();
System.out.println(ms.min());
}
} class MinStack{ private Stack minStack = new Stack(); private Stack stack = new Stack(); public int pop(){
minStack.pop(); return stack.pop();
} public void push(int num){ if(minStack.size()<=0){
minStack.push(num); return;
}
Integer min = minStack.lastElement(); if(num
minStack.push(num);
} else{
minStack.push(min);
}
stack.push(num);
} public int min(){ if(minStack.size()<=0){ return -1;
} return minStack.lastElement();
}
}
题目七：
//找出数组中出现次数大于一半的数 @Test public void test(){ int[] num = {1,2,2,2,2,2,2,4,2,4,6,4,2,6,8,2,7,7};
System.out.println(moreThanHaft(num));
} public int moreThanHaft(int[] num){ int result = -1; int times = 0; for(int i=0;i
result = num[i];
times++;
} else{ if(num[i]==result){
times++;
} else{
times--;
}
}
} return result;
}
题目八：
//判断一个数组是否是另一个栈的出栈顺序 @Test public void test(){ int[] num = {1,2,3,4,5}; //int[] num1={1,2,3,5,4}; int[] num2={2,1,5,3,4};
Stack s1 = new Stack();
Stack s2 = new Stack(); for(int i=0;i<5;i++){
s2.push(num2[i]);
}
System.out.println(testOrder(num,s1,s2));
} public boolean testOrder(int[] num,Stack s1,Stack s2){ int length = num.length; for(int i=0;i
s1.push(num[i]); int s2Num = s2.lastElement(); if(s2Num==s1.lastElement().intValue()){
s1.pop();
s2.pop();
}
} while(!s1.isEmpty()){ if(!s1.pop().equals(s2.pop())){ return false;
}
} return true;
}
题目九：
//从扑克牌抽5张牌，0可以为任意数，判断是否是顺子 @Test public void test(){ int[] num = {0,1,5,3,2};
System.out.println(check(num));
} public boolean check(int[] num){ //0-13 int[] pai = new int[14]; for(int n : num){
pai[n]+=1;
}
qsort(num,0,num.length-1); int count = pai[0]; int start = 0; if(num[0]==0){
start=num[1];
} else{
start=num[0];
} for(int i = start;i<=start+5;i++){ if(pai[i]>1)return false;
count += pai[i];
} if(count == 5)return true; else return false;
} public void qsort(int[] num,int left,int right){ if(left
qsort(num,left,partition-1);
qsort(num,partition+1,right);
}
} public int partition(int[] num,int left,int right){ int partition = num[left]; while(left=partition){
right--;
}
swap(num,left,right); while(left
left++;
}
swap(num,left,right);
} return left;
} public void swap(int[] num,int m,int n){ int temp = num[m];
num[m]=num[n];
num[n]=temp;
}
题目十：
//输出第k个丑数(因子只有2，3，5) @Test public void test(){
findUglyNum(8);
} public void findUglyNum(int index){ int[] num = new int[index]; int next = 1;
num[0]=1; int index2=0; int index3=0; int index5=0; while(next
num[next] = getSuitable(num2,num3,num5); while(num[index2]*2<=num[next]){
index2++;
} while(num[index3]*3<=num[next]){
index3++;
} while(num[index5]*5<=num[next]){
index5++;
}
next++;
}
System.out.println(num[index-1]);
} public int getSuitable(int num2,int num3,int num5){ int s = num2; if(num3
s = num3;
} if(num5
s = num5;
} return s;
}