经典算法_杨辉三角，集合法

经典算法_杨辉三角，集合法

代码编写环境:VSCode2017

杨辉三角:

#include<stdio.h>

int main() {
	int a[10][10];
	int i,j;
	//1、给二维数组赋初值
	for (i = 0; i < 10; i++)
	{
		for (j = 0; j <= i; j++)
		{
			a[i][j] = 0;
		}

	}

	//2、给二维数组的第一列和对角线赋值1
	for (i = 0; i < 10; i++)
	{
		a[i][0] = 1;
		a[i][i] = 1;
	}

	//3、按照杨辉三角规律，进行循环运算
	/*	1
		1	1	
		1	2	1
		1	3	3	1
		a[2][1] = a[1][0] + a[1][1]
				||
		a[2][1] = a[2-1][1-1] + a[2-1][1]
	*/
	for (i = 2; i < 10; i++)
	{
		for ( j = 1; j < i; j++)
		{
			a[i][j] = a[i - 1][j - 1] + a[i - 1][j];
		}

	}

	//4、打印结果
	for (i = 0; i < 10; i++)
	{
		for (j = 0; j <= i; j++)
		{
			printf("%5d",a[i][j]);
		}
		printf("
");
	}
}


================指针比较三数法================

#include<stdio.h>

void swap(int *,int *);
int main(){

    int a,b,c;
    a = 3;
    b = 2;
    c = 1;
    int *p1,*p2,*p3;



    p1 = &a;
    p2 = &b;
    p3 = &c;

    if(a>b){
        swap(p1,p2);
    }
    if(a>c){
        swap(p1,p3);
    }
    if(b>c){
        swap(p3,p2);
    }

    printf("%d	%d	%d",a,b,c);

}

void swap(int *s1,int *s2){
    int t;
    t = *s1;
    *s1 = *s2;
    *s2 = t;
}

结果:

Java底层是C，语言对比一下，会更好。

JVM的本地方法栈

1.c语言的int类型数组默认赋初值-858993460,java则赋0。
2.c语言的int a[10][10];的长度不能为变量，只能是常量,java则可以, int[] arr = new int[n];

Java语言:

代码编写环境:IDEA2018

数组法

package com.m.suan_pai;


import java.util.Scanner;

public class Test2 {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        System.out.println("请属于一个大于0的整数");
        int n = scanner.nextInt();
        if (n <= 0) {
            throw new NumberFormatException(n + "<=0");
        }
        test(n);
    }

    public static void test(int n) {
        int[][] a = new int[n][n];
        for (int i = 0; i < n; i++) {
            a[i][0] = 1;
            a[i][i] = 1;
        }
        for (int i = 2; i < n; i++) {
            for (int j = 1; j < i; j++) {
                a[i][j] = a[i - 1][j - 1] + a[i - 1][j];
            }

        }

        //4、打印结果
        for (int i = 0; i < n; i++) {
            for (int j = 0; j <= i; j++) {
                System.out.printf("%5d", a[i][j]);
            }
            System.out.printf("
");
        }
    }


}

集合法:

package com.m.pascals_triangle;

import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;

public class PascalsTriangle_List {

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        System.out.println("请输入:");
        int n = scanner.nextInt();
        for (List<Integer> list : generate(n)) {
            System.out.println(list);
        }
    }

    public static List<List<Integer>> generate(int numRows) {

        if (numRows <= 0) {
            throw new NumberFormatException(numRows + "<=0");
        }

        List<List<Integer>> lists = new ArrayList<>();
        lists.add(new ArrayList<>());
        lists.get(0).add(1);

        if (numRows == 0) {
            return lists;
        }

        for (int i = 1; i < numRows; i++) {
            List<Integer> list = new ArrayList<>();

            List<Integer> preList = lists.get(i - 1);
            list.add(1);

            for (int j = 1; j < i; j++) {
                int result = preList.get(j - 1) + preList.get(j);
                list.add(result);
            }

            list.add(1);
            lists.add(list);

        }
        return lists;
    }

}