algorithm头文件下常用函数

#include <iostream>
#include <vector>
#include <algorithm>
#include <cstdio>

using namespace std;

struct Node{
    int num;
    string name;

    Node(int num, string name){
        this->num = num;
        this->name = name;
    }
};

bool cmp(Node n1, Node n2){
    return n1.num > n2.num; // 升序
}


// 有两个需要比较的字段时
struct node{
    int x, y;
};

bool cmp2(node n1, node n2){
    if(n1.x!=n2.x){
        return n1.x < n2.x;
    }

    return n1.y > n2.y;
}

int main(){

    int x = 10, y = 20;

    printf("%d\n", max(x, y));
    printf("%d\n", min(x, y));

    swap(x, y);

    printf("x: %d, y: %d\n", x, y);

    int a[5] = {1, 2, 3, 4, 5};

    // 不能在这之前对a数组调用reverse
    // 全排列
    do{

        printf("%d %d %d %d %d\n", a[0], a[1], a[2], a[3], a[4]);

    }while (next_permutation(a, a + 5));

    vector<int> v = {53, 23, 3, 5, 36, 7};

    // [it, it2)
    reverse(a, a + 5);
    reverse(v.begin(), v.end());

    for (int i = 0; i < 5; ++i) {
        printf("%d ", a[i]);
    }

    printf("\n");

    for (int i = 0; i < v.size(); ++i) {
        printf("%d ", v[i]);
    }

    printf("\n");

    // 将[a, a+5)填充为123
    fill(a, a + 5, 123);

    for (int i = 0; i < 5; ++i) {
        printf("%d ", a[i]);
    }

    printf("\n");

    // [s, e)
    sort(v.begin(), v.end());

    for (int i = 0; i < v.size(); ++i) {
        printf("%d ", v[i]);
    }

    vector<Node> vn;

    // 结构体对象的两种创建
    Node * n1 = new Node(3, "xiaowang");
    Node * n2 = new Node(4, "xiaoli");
    Node * n3 = new Node(1, "xiaomei");

    Node n4 = {83, "dd"};

    vn.push_back(*n1);
    vn.push_back(*n3);
    vn.push_back(*n2);
    vn.push_back(n4);

    sort(vn.begin(), vn.end(), cmp);

    printf("\n");
    for (int i = 0; i < vn.size(); ++i) {
        printf("%d %s\n", vn[i].num, vn[i].name.c_str());
    }

    // 必须有序
    int arr[10] = {1, 2, 3, 4, 4, 5, 5, 6, 6, 10};

    // [s, e) 范围内第一个值大于等于val的元素的位置,返回指针或迭代器
    int * p1 = lower_bound(arr, arr + 10, 3);
    // [s, e) 范围内第一个值大于val的元素的位置,返回指针或迭代器
    int * p2 = upper_bound(arr, arr + 10, 3);

    // 对应的索引为
    printf("ind: %d ", p1 - arr);
    printf("val: %d \n", *p1);
    printf("ind: %d ", p2 - arr);
    printf("val: %d ", *p2);

    vector<int> vv = {1, 2, 3, 4, 5};

    vector<int>::iterator it = upper_bound(vv.begin(), vv.end(), 3);

    printf("\nval: %d ind: %d", *it, it - vv.begin());

    return 0;
}