Intersecting Intervals

AtCoder

IDabc355_d

Time3000ms

Memory256MB

Difficulty—

You are given $N$ intervals of real numbers. The $i$\-th $(1 \leq i \leq N)$ interval is $[l_i, r_i]$. Find the number of pairs $(i, j)\,(1 \leq i < j \leq N)$ such that the $i$\-th and $j$\-th intervals intersect. ## Constraints * $2 \leq N \leq 5 \times 10^5$ * $0 \leq l_i < r_i \leq 10^9$ * All input values are integers. ## Input The input is given from Standard Input in the following format: $N$ $l_1$ $r_1$ $l_2$ $r_2$ $\vdots$ $l_N$ $r_N$ [samples]

Samples

Input #1

Output #1

2

The given intervals are $[1,5], [7,8], [3,7]$. Among these, the $1$\-st and $3$\-rd intervals intersect, as well as the $2$\-nd and $3$\-rd intervals, so the answer is $2$.

Input #2

Output #2

Input #3

2
1 2
3 4

Output #3

API Response (JSON)

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  "problem": {
    "name": "Intersecting Intervals",
    "description": {
      "content": "You are given $N$ intervals of real numbers. The $i$\\-th $(1 \\leq i \\leq N)$ interval is $[l_i, r_i]$. Find the number of pairs $(i, j)\\,(1 \\leq i < j \\leq N)$ such that the $i$\\-th and $j$\\-th interv",
      "description_type": "Markdown"
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    "platform": "AtCoder",
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      "memory_limit": 262144
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    "difficulty": "None",
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  "statements": [
    {
      "statement_type": "Markdown",
      "content": "You are given $N$ intervals of real numbers. The $i$\\-th $(1 \\leq i \\leq N)$ interval is $[l_i, r_i]$. Find the number of pairs $(i, j)\\,(1 \\leq i < j \\leq N)$ such that the $i$\\-th and $j$\\-th interv...",
      "is_translate": false,
      "language": "English"
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