739. Daily Temperatures

Given daily temperatures, return an array where answer[i] is the number of days after day i until a warmer temperature, or 0 if there is none.

Keep a stack of days still waiting for a warmer one; their temperatures decrease from bottom to top. A warmer day pops every cooler day off the top and answers it.

1function dailyTemperatures(temps: number[]): number[] {
2  const res = new Array(temps.length).fill(0), stack: number[] = [];
3  for (let i = 0; i < temps.length; i++) {
4    while (stack.length && temps[stack.at(-1)!] < temps[i]) {
5      const j = stack.pop()!;
6      res[j] = i - j;
7    }
8    stack.push(i);
9  }
10  return res;
11}

temperatures

stack (waiting days)

empty

answer

Day 0: 73°.

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