PAT (Advanced) 1048. Find Coins (25)

原题：1048. Find Coins (25)

解题思路：
双指针法。先将所有的数从小到大排序，左右指针分别指向最左和最右，若两个值之和比要求的大，右指针前移，小则左指针后移。

代码如下：#include<cstdio>
#include<algorithm>
#include<cstring>
using namespace std;
const int maxn = 100000 + 5;
int coin[maxn];

int main()
{
int n, m;
while(scanf("%d%d", &n, &m) == 2)
{
for(int i = 0; i < n; i++)
scanf("%d", &coin[i]);
sort(coin, coin+n);
int l = 0, r = n-1;
while(l < r)
{
if(coin[l] + coin[r] > m) r--;
else if(coin[l] + coin[r] < m) l++;
else {printf("%d %d\n", coin[l], coin[r]); break;}
}
if(l == r) printf("No Solution\n");
}
return 0;
}