二分搜索（int类型） C++版本 python版本

AcWing 789数的范围

https://www.acwing.com/problem/content/791/

 

#include 
#include 
#include 

using namespace std;

const int N = 1e5 + 5;

int a[N];

int x;

int binSearchLeft(int L, int R)
{
    while(L < R)
    {
        int mid = L + R >> 1;
        if(a[mid] >= x) R = mid;
        else    L = mid + 1;
    }
    if(a[L] == x)
        return L;
    else
        return -1;
}

int binSearchRight(int L, int R)
{
    while(L < R)
    {
        int mid = L + R + 1>> 1;
        if(a[mid] <= x) L = mid;
        else    R = mid - 1;
    }
    if(a[L] == x)
        return L;
    else
        return -1;
}

int main()
{
    int n, q;
    scanf("%d%d", &n, &q);
    for(int i = 0; i < n; ++ i)
        scanf("%d", &a[i]);
    while(q --)
    {
        scanf("%d", &x);
        int L = binSearchLeft(0, n - 1);
        int R = binSearchRight(0, n - 1);
        printf("%d %d\n", L, R);
    }
    return 0;
}

 

n, q = map(int, input().split())
a = list(map(int, input().split()))


def binarySearchLeft(k, L, R):
    while L < R:
        mid = L + R >> 1
        if a[mid] >= k:
            R = mid
        else:
            L = mid + 1
    if a[L] != k:
        return -1
    else:
        return L


def binarySearchRight(k, L, R):
    while L < R:
        mid = L + R + 1 >> 1
        if a[mid] <= k:
            L = mid
        else:
            R = mid - 1
    if a[L] != k:
        return -1
    return L


while q:
    k = int(input())
    L = binarySearchLeft(k, 0, n - 1)
    R = binarySearchRight(k, 0, n - 1)
    print(L, R)
    q -= 1