class Solution:
    def maxProfit(self, prices):
        buy = prices[0]
        profit = 0
        for p in prices[1:]:
            profit = max(profit, p - buy)
            buy = min(buy, p)
        return profit

function mergeSort(arr) {
  if (arr.length <= 1) return arr;
  const mid = arr.length >> 1;
  const L = mergeSort(arr.slice(0, mid));
  const R = mergeSort(arr.slice(mid));
  return merge(L, R);
}

int dijkstra(int src, int dst) {
  priority_queue<pii, v<pii>, greater<>> pq;
  dist[src] = 0;
  pq.push({0, src});
  while (!pq.empty()) {
    auto [d, u] = pq.top(); pq.pop();
    if (d > dist[u]) continue;
  }
}

const hashMap = {};
for (let i = 0; i < s.length; i++) {
  hashMap[s[i]] = (hashMap[s[i]] || 0) + 1;
}
return Object.entries(hashMap)
  .sort((a,b) => b[1]-a[1])[0][0];

def longestCommonSubsequence(s1, s2):
    m, n = len(s1), len(s2)
    dp = [[0]*(n+1) for _ in range(m+1)]
    for i in range(1,m+1):
        for j in range(1,n+1):
            if s1[i-1]==s2[j-1]: dp[i][j]=dp[i-1][j-1]+1
            else: dp[i][j]=max(dp[i-1][j],dp[i][j-1])
    return dp[m][n]