Ice Cream Parlor
Problem Statement
Sunny and Johnny together have N flavors, and they want to choose two flavors so that they end up spending the whole amount.
You are given the cost of these flavors. The cost of the M.
Input Format
The first line of the input contains i.
Output Format
Output two integers, each of which is a valid index of a flavor. The lower index must be printed first. Indices are indexed from N.
Constraints
]
The prices of any two items may be the same and each test case has a unique solution.
Sample Input
2
4
5
1 4 5 3 2
4
4
2 2 4 3
Sample Output
1 4
1 2
Explanation
The sample input has two test cases.
For the 1st, the amount M = 4 and there are 5 flavors at the store. The flavors indexed at 1 and 4 sum up to 4.
For the 2nd test case, the amount M = 4 and the flavors indexed at 1 and 2 sum up to 4.
Solution
简单题。
利用题目给出的cost数组构造index数组，index[i]表示i在cost数组中首次出现的位置。
Implementation
#include<bits/stdc++.h>
using namespace std;
const int N(1e4+5);
int idx[N];
int main(){
freopen("in", "r", stdin);
int T;
cin>>T;
for(int n, m, id1, id2; T--; memset(idx, 0, sizeof(idx))){
cin>>m>>n;
for(int i=1, c; i<=n; i++){
cin>>c;
if(c>=m) continue; //error-prone
if(!idx[c]) idx[c]=i;
if(idx[m-c]&&idx[m-c]!=i){
id1=idx[m-c], id2=i; //error-prone
}
}
cout<<id1<<' '<<id2<<endl;
}
}
凡注释error-prone的地方都是开始写错了的。
1. 我的写法是边读入边处理的，有时会没读完就得出答案，这时很容易就来个break;
2. 针对这道题的
2.1 要预判c>=m的情况
2.2 如何处理cost相同的flavor