class Solution {
public:
struct Status {
int lSum, rSum, mSum, iSum;
};
Status pushUp(Status l, Status r) {
int iSum = l.iSum + r.iSum;
int lSum = max(l.lSum, l.iSum + r.lSum);
int rSum = max(r.rSum, r.iSum + l.rSum);
int mSum = max(max(l.mSum, r.mSum), l.rSum + r.lSum);
return (Status) {lSum, rSum, mSum, iSum};
};
Status get(vector &a, int l, int r) {
if (l == r) {
return (Status) {a[l], a[l], a[l], a[l]};
}
int m = (l + r) >> 1;
Status lSub = get(a, l, m);
Status rSub = get(a, m + 1, r);
return pushUp(lSub, rSub);
}
int maxSubArray(vector& nums) {
return get(nums, 0, nums.size() - 1).mSum;
}
};
这是力扣第53道最大子数组和中的官方解答的第二个方法,分治法,我明白他说的线段数树的意思,但是我的逻辑盘不过来。
来一个负责任的大佬,详细讲解一下Status pushUp(Status l, Status r) {
int iSum = l.iSum + r.iSum;
int lSum = max(l.lSum, l.iSum + r.lSum);
int rSum = max(r.rSum, r.iSum + l.rSum);
int mSum = max(max(l.mSum, r.mSum), l.rSum + r.lSum);
return (Status) {lSum, rSum, mSum, iSum};
};这段代码,希望能通俗易懂一点,主要是逻辑,我自己内心演算算出不来,例如int lSum = max(l.lSum, l.iSum + r.lSum);中我感觉l.lSum不合理我觉得得用l.mSum,int lSum = max(l.lSum, l.iSum + r.lSum);
int rSum = max(r.rSum, r.iSum + l.rSum);而且我觉得会重叠在l.Sum和rsum中。最好能结合线段树讲解一下