求助！全为RE，本地跑没问题，也用的是二分。

Marlin_Phone @ 2024-12-02 23:39:23

// https://www.luogu.com.cn/problem/P2249
#define _CRT_SECURE_NO_WARNINGS
#include <iostream>
#include <cmath>
#include <vector>
using namespace std;

bool isblue(int num, int temp) {
    if(num < temp) return true;
    else return false;
}
int main(){
    int n, m, temp; 
    scanf("%d%d", &n, &m);
    vector<int> num(n + 10);

    for (int i = 1; i <= n; i++) {
        scanf("%d", &num[i]);
    }
    for (int i = 0; i < n; i++) {
        scanf("%d", &temp);
        int l = 0, r = n + 1;
        while (l + 1 != r) {
            int mid = (l + r) / 2;
            if (isblue(num[mid], temp) == true) l = mid;
            else r = mid;
        }
        if(num[r] == temp) printf("%d ", r);
        else printf("-1 ");
    }

    return 0;
}

by Marlin_Phone @ 2024-12-02 23:41:36

孩子刚学完，做的第一道二分，问它也说没问题，求助 T_T

by pjh0625 @ 2024-12-03 06:23:10

@Marlin_Phone

#include<bits/stdc++.h>
using namespace std;
long long n,m,a[1000001],x,t;
int f(int t,int w,int x){
    while(t<=w){
        int mid=(t+w)/2;
        if(a[mid]>=x){
            w=mid-1;
        }else{
            t=mid+1;
        }
    }
    if(t>n) return -1;
    if(a[t]!=x) return -1;
    return t;
}
int main(){
    cin>>n>>m;
    for(int i=1;i<=n;i++) scanf("%d",&a[i]);
    for(int i=1;i<=m;i++){
        scanf("%d",&x);
        printf("%d ",f(1,n,x));
    }
    return 0;
}

我做的似乎有点复杂。。。

by Marlin_Phone @ 2024-12-05 21:58:52

@pjh0625 唉，我也知道这种写法，但是实在检查不出来自己到底错哪了 T_T 谢谢你

by pjh0625 @ 2024-12-05 22:15:44

@Marlin_Phone 我换种方法做了下，似乎是您的方法吧 。。。

#include <bits/stdc++.h>
using namespace std;
int main(){
    int n, m, q;    
    scanf("%d%d", &n, &m);
    int num[n];  
    int f[m]; 
    for (int i = 0; i < n; i++) {
        scanf("%d", &num[i]);
    }
    for (int i = 0; i < m; i++) {
        scanf("%d", &q);
        int l = 0, r = n;
        while (l < r) {
            int mid = (l + r) / 2;
            if (num[mid] < q) {
                l = mid + 1;
            } else {
                r = mid; 
            }
        }
        if (l < n && num[l] == q) {
            f[i] = l + 1;
        } else {
            f[i] = -1;
        }
    }
    for (int i = 0; i < m; i++) {
        printf("%d ", f[i]);
    }

    return 0;
}

by pjh0625 @ 2024-12-05 22:17:50

我自学的，如有不足多包涵及指正