数列极差

Posted 2022-11-16 liuzz-20180701

题目描述

思路

代码

#include <cstdio>
#include <algorithm>
#include <cstring>
using namespace std;
int n, arr[50005], save[50005];
int tmp[50005];
long long  maxx, minn;
const int inf = 0x7fffffff;
inline int read() 
    int s = 0, f = 1;
    char ch = getchar();
    while (ch < '0' || ch > '9') 
        if (ch == '-') f = -1;
        ch = getchar();
    
    while (ch >= '0' && ch <= '9') s = s * 10 + ch - '0', ch = getchar();
    return s * f;

int cmpa(int a, int b) 
    return a < b;

int cmpb(int a, int b) 
    return a > b;

void inserta(int * arr, int tot, int key) 
    for (int i = tot; i >= 0; --i) 
        if (arr[i] > key) arr[i + 1] = arr[i]; 
        else 
            arr[i + 1] = key;
            break;
        
    

void insertb(int * arr, int tot, int key) 
    for (int i = tot; i >= 0; --i) 
        if (arr[i] < key) arr[i + 1] = arr[i]; 
        else 
            arr[i + 1] = key;
            break;
        
    

void show(int * r, int n) 
    for (int i = 1; i <= n; ++i) 
        printf("%d ", r[i]);
    
    puts("");

int main() 
    n = read();
    for (int i = 1; i <= n + 1; ++i) arr[i] = read();
    memcpy(save, arr, sizeof(arr));
    sort(arr + 1, arr + 1 + n, cmpa);
    for (int i = n; i >= 3; --i) 
        for (int j = 1; j <= i - 2; ++j) tmp[j] = arr[j + 2];
        inserta(tmp, i - 2, arr[1] * arr[2] + 1);
        for (int j = 1; j <= i - 1; ++j) arr[j] = tmp[j];  
    
    maxx = arr[1] * arr[2] + 1;
    memcpy(arr, save, sizeof(arr));
    sort(arr + 1, arr + n + 1, cmpb);
    for (int i = n; i >= 3; --i) 
        for (int j = 1; j <= i - 2; ++j) tmp[j] = arr[j + 2];
        tmp[0] = inf;
        insertb(tmp, i - 2, arr[1] * arr[2] + 1);
        for (int j = 1; j <= i - 1; ++j) arr[j] = tmp[j];
    
    minn = arr[1] * arr[2] + 1;
    printf("%lld\n", maxx - minn);
    return 0;