#1 WA 萌新刚学二分 求助

XuYu0317 @ 2024-01-13 09:32:53

#include<bits/stdc++.h>

using namespace std;
const int N = 1000010;
int n, m;
int q[N];
int main(){
    scanf("%d%d", &n, &m);
    for (int i = 1; i <= n; i++) scanf ("%d", &q[i]);

    while(m--) {
        int x;
        scanf("%d", &x);

        int l = 0, r = n;
        while (l < r) {
            int mid = l + (r - l) / 2;
            if (q[mid] >= x) r = mid;
            else l = mid + 1;
        }

        if (q[l] == x) printf("%d ", l);
        else printf("-1 ");
    }

    return 0;
}

by danlao @ 2024-01-13 09:40:52

看不出来问题，你看看我的代码吧

#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
const int N=1e6+10;
ll m,n;
ll a[N],x[N],l,s[N];
int find(int d,int n){
    ll l=1,r=n,ans=-1;
    while(l<=r){
        ll mid=(l+r)/2;
        if(a[mid]==d){
            ans=mid;
            r=mid-1;
        }
        else if(a[mid]<d) l=mid+1;
        else if(a[mid]>d) r=mid-1;
    }
        return ans;
}
int main(){
    scanf("%lld%lld",&n,&m);
    for(int i=1;i<=n;i++) scanf("%lld",&a[i]);
    for(int i=1;i<=m;i++){
        scanf("%lld",&x[i]);
        s[i]=find(x[i],n);
    }
    for(int i=1;i<=m;i++) printf("%lld ",s[i]);
    return 0;
}

by xiaoshumiao @ 2024-01-13 09:50:02

@XuYu0317

int l = 0, r = n;

改成：

int l = 1, r = n;

就行了。

by XuYu0317 @ 2024-01-13 09:50:37

找到错误了 第15行

l = 0

应为

l = 1

by XuYu0317 @ 2024-01-13 09:51:03

@yaodiguoan 感谢您提供参考

by XuYu0317 @ 2024-01-13 09:51:41

此贴结

by XuYu0317 @ 2024-01-13 09:52:30

@xiaoshumiao 感谢您的帮助

by danlao @ 2024-01-13 10:26:34

@XuYu0317 不客气