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[20220822] day1 prefix sum 문제 풀이

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	`1`	`+https://leetcode.com/study-plan/`

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	`1`	`+https://leetcode.com/study-plan/leetcode-75/?progress=xxpdgksv`

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	`1`	`+# https://leetcode.com/problems/find-pivot-index/`
	`2`	`+# 724. Find Pivot Index`
	`3`	`+from typing import List`
	`4`	`+`
	`5`	`+`
	`6`	`+class Solution:`
	`7`	`+ def pivotIndex(self, nums: List[int]) -> int:`
	`8`	`+ total = sum(nums)`
	`9`	`+ left_sum = 0`
	`10`	`+`
	`11`	`+ for i in range(len(nums)):`
	`12`	`+ if left_sum == (total - nums[i] - left_sum):`
	`13`	`+ return i`
	`14`	`+ left_sum += nums[i]`
	`15`	`+ return -1`
	`16`	`+`
	`17`	`+`
	`18`	`+if __name__ == '__main__':`
	`19`	`+ sol = Solution()`
	`20`	`+ print(sol.pivotIndex([1, 7, 3, 6, 5, 6]))`
	`21`	`+ print(sol.pivotIndex([1, 2, 3]))`
	`22`	`+ print(sol.pivotIndex([2, 1, -1]))`
	`23`	`+ # 사실 아래 케이스에서는 안돌아가는데 코드는 통과가 됨...`
	`24`	`+ # https://leetcode.com/problems/find-pivot-index/discuss/136167/This-is-a-very-poorly-described-problem`
	`25`	`+ print(sol.pivotIndex([-1, -1, -1, 0, 1, 1]))`

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	`1`	`+# https://leetcode.com/problems/running-sum-of-1d-array/`
	`2`	`+# 1480. Running Sum of 1d Array`
	`3`	`+from typing import List`
	`4`	`+`
	`5`	`+`
	`6`	`+class Solution:`
	`7`	`+ def runningSum(self, nums: List[int]) -> List[int]:`
	`8`	`+`
	`9`	`+ for i in range(1, len(nums)):`
	`10`	`+ nums[i] += nums[i-1]`
	`11`	`+ return nums`

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