PAT 1048. Find Coins

#include <cstdio>
#include <cstdlib>
#include <vector>
#include <algorithm>

using namespace std;

int main() {
    int N, M;
    scanf("%d%d", &N, &M);
    
    vector<int> coins(N);
    for (int i=0; i<N; i++) {
        scanf("%d", &coins[i]);
    }
    
    sort(coins.begin(), coins.end());
    
    int p = 0, q = N - 1;
    while (p<q) {
        int sum = coins[p] + coins[q];
        if (sum > M) {
            // bigger, so decrease it, move q to the smaller coins
            q--;
        } else if (sum < M) {
            // smaller, so increase it, move p to the bigger coins
            p++;
        } else {
            // we found the coins
            printf("%d %d\n", coins[p], coins[q]);
            break;
        }
    }
    if (p >= q) {
        printf("No Solution\n");
    }
    return 0;
}