Words & Expressions

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Words & Expressions

• if the string can be segmented into a space-separated sequence of one or more given words
• given an array of distinct integers
• return the number of possible combinations that add up to target.
• The robot is initially located at the top-left corner of the board. The robot tries to move to the bottom-right corner
• the answer fits in a 32-bit integer
• a two-dimensional array
• You may assume all four edges of the grid are all surrounded by water.
• Rotate an object clockwise, or counterclockwise
• You have to rotate the image in-place, which means you have to modify the input 2D matrix directly. DO NOT allocate another 2D matrix and do the rotation.
• it can be actually treated as a sub-problem

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• in the opposite direction, in reverse (opposite) order
• the right-most column
• the outer (most) layer
• save the value in a temporary variable
• left & right boundary, top & bottom boundary

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• O(√x) - square root of n
• O(n^2) - n square time
• O(n^3) - n cubed time
• O(2^n) - 2 to the n
• O(x^y) - x to the y
• O(n!) - n factorial
• O(1) - the memory (space) complexity is constant
• n' - n prime
• the dimension nxn (n by n)

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• (: opening parentheses, ): closing parentheses
• [: opening square bracket, ]: closing square bracket
• {: opening curly bracket, }: closing curly bracket

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• ancestor node
• descendant node