各位佬！为什么vector过不了，用数组却可以以

whho_0 @ 2024-02-23 17:42:36

#include<iostream>
#include<vector>
using namespace std;
int findx(vector<int> nums,int target,int n) {
    int low = 0, high = n;
    while (low <= high) {
        int mid = low + (high - low) / 2;
        if (nums[mid] >= target) {
            high = mid - 1;
        }
        else {
            low = mid + 1;
        }
    }
    if (low > n-1 || nums[low] != target) {
        return -1;
    }
    else {
        return low+1;
    }
}

int main() {
    int n, m;
    cin >> n >> m;
    vector<int> nums(n);
    for (int i = 0; i < n; i++) {
        cin >> nums[i];
    }
    for (int i = 0; i < m; i++) {
        int x;
        cin >> x;
        cout << findx(nums,x,n) << " ";
    }
    return 0;
}

by TCIC_4294967296 @ 2024-02-23 18:38:01

因为vector在函数传参时会O(n)复制整个数组，普通数组只会传地址，把vector改成引用传递即可。

修改后：

#include<iostream>
#include<vector>
using namespace std;
int findx(vector<int>& nums,int target,int n) {
    int low = 0, high = n;
    while (low <= high) {
        int mid = low + (high - low) / 2;
        if (nums[mid] >= target) {
            high = mid - 1;
        }
        else {
            low = mid + 1;
        }
    }
    if (low > n-1 || nums[low] != target) {
        return -1;
    }
    else {
        return low+1;
    }
}

int main() {
    int n, m;
    cin >> n >> m;
    vector<int> nums(n);
    for (int i = 0; i < n; i++) {
        cin >> nums[i];
    }
    for (int i = 0; i < m; i++) {
        int x;
        cin >> x;
        cout << findx(nums,x,n) << " ";
    }
    return 0;
}

by TCIC_4294967296 @ 2024-02-23 18:39:33

@TCIC_4294967296 亲测可AC