53. Maximum Subarray
同121题.
Find the contiguous subarray within an array (containing at least one number) which has the largest sum.
For example, given the array [-2,1,-3,4,-1,2,1,-5,4]
,
the contiguous subarray [4,-1,2,1]
has the largest sum = 6
.
人家媳妇:
(O(n)) time, (O(1)) space.
想法:子序列若小于0,还不如重新设定子序列,既,通过 max(f+A[i],A[i])
就可以搞定.
int maxSubArray(vector<int>& A) {
int n = A.size();
if (n == 0) return 0;
int re = A[0], sum = 0, i;
for (i = 0; i < n; i++) {
sum += A[i];
re = sum > re ? sum : re; //re 始终存着最大子序列的和
sum = sum > 0 ? sum : 0; //重新设定子序列
}
return re;
}
这帮变态还应用了动态规划方法((DP approach)).