leetcode 1013. 将数组分成和相等的三个部分(Partition Array Into Three Parts With Equal Sum)
题目描述:
给定一个整数数组 A
,只有我们可以将其划分为三个和相等的非空部分时才返回 true
,否则返回 false
。
形式上,如果我们可以找出索引 i+1 < j
且满足 (A[0] + A[1] + ... + A[i] == A[i+1] + A[i+2] + ... + A[j-1] == A[j] + A[j-1] + ... + A[A.length - 1])
就可以将数组三等分。
示例 1:
输出:[0,2,1,-6,6,-7,9,1,2,0,1]
输出:true
解释:0 + 2 + 1 = -6 + 6 - 7 + 9 + 1 = 2 + 0 + 1
示例 2:
输入:[0,2,1,-6,6,7,9,-1,2,0,1]
输出:false
示例 3:
输入:[3,3,6,5,-2,2,5,1,-9,4]
输出:true
解释:3 + 3 = 6 = 5 - 2 + 2 + 5 + 1 - 9 + 4
提示:
3 <= A.length <= 50000
-10000 <= A[i] <= 10000
解法:
class Solution {
public:
bool canThreePartsEqualSum(vector<int>& A) {
int sum_val = 0;
for(int val : A){
sum_val += val;
}
if(sum_val % 3 != 0){
return false;
}else{
int one = sum_val /3;
int two = one*2;
bool first = false, second = false;
int pre = 0;
for(int val : A){
pre += val;
if(pre == one){
first = true;
}else if(pre == two && first == true){
return true;
}
}
return false;
}
}
};