求助，二分板子不知道为什么全是RE，大佬们帮帮忙

FengYue_Yu @ 2023-04-03 10:43:38

#include<iostream>
using namespace std;
int a[100005];

int find(int n,int f)
{
    int l=1,r=n;
    while(l<=r)
    {
        int mid=l+r>>1;
        if(a[mid]>=f)
            r=mid;
        else
            l=mid+1;
    }
    if(a[l]==f)
        return l;
    else
        return -1;
}

int main()
{
    int n,m;
    while(cin>>n>>m)
    {
        for(int i=1;i<=n;i++)
            cin>>a[i];
        while(m--)
        {
            int f;
            cin>>f;
            cout<<find(n,f)<<" ";
        }
        cout<<endl;
    }
}

by FengYue_Yu @ 2023-04-03 10:51:04

之前数组开小了，加大数组后就全都是TLE了

#include<iostream>
using namespace std;
int a[1000005];

int find(int n,int f)
{
    int l=1,r=n;
    while(l<=r)
    {
        int mid=l+(r-l)/2;
        if(a[mid]>=f)
            r=mid;
        else
            l=mid+1;
    }
    if(a[l]==f)
        return l;
    else
        return -1;
}

int main()
{
    int n,m;
    while(cin>>n>>m)
    {
        for(int i=1;i<=n;i++)
            cin>>a[i];
        while(m--)
        {
            int f;
            cin>>f;
            cout<<find(n,f)<<" ";
        }
    }
}

by FengYue_Yu @ 2023-04-03 10:52:36

麻了，把边界条件改错了，把

while(l<=r)

改成

while(l<r)

就可以了

by Zpril_20211017 @ 2023-04-03 10:57:56

@FengYue_Yu stl

#include <bits/stdc++.h>
using namespace std;

int a[1000001];

int main()
{
    int n,m;
    cin >> n >> m;
    for(int i = 1;i <= n;i++)
        cin >> a[i];
    for(int i = 1;i <= m;i++)
    {
        int c;
        cin >> c;
        int l = lower_bound(a + 1,a + n + 1,c) - a;
        if(a[l] == c)
            cout << l << ' ';
        else
            cout << -1 << ' ';
    }
    return 0;
}