Number of smooth descent periods of a stock

Array Math Two Pointers Dynamic Programming Sliding Window

67.7% acceptance

Feb 25, 2026

1076

You are given an integer array prices representing the daily price history of a stock, where prices[i] is the stock price on the ith day. A smooth descent period of a stock consists of one or more contiguous days such that the price on each day is lower than the price on the preceding day by exactly 1. The first day of the period is exempted from this rule. Return the number of smooth descent periods.

Solution

Rust

Time O(n)

Space O(1)

LeetCode

solution.rs

impl Solution {
  pub fn get_descent_periods(prices: Vec<i32>) -> i64 {
    let mut ans = 0i64;
    let mut run = 0i64;
    for i in 0..prices.len() {
      if i > 0 && prices[i] == prices[i - 1] - 1 {
        run += 1;
      } else {
        run = 1;
      }
      ans += run;
    }
    ans
  }
}