1. Two Sum - LeetCode
阿新 • • 發佈:2018-06-17
rip lB num 其他 思路 int href 簡單 integer
Question
1. Two Sum
Solution
思路很簡單這裏就不說了,下面貼了不同的幾個Java實現的時間與其他算法實現的時間的比較
這個是LeetCode的第一道題,也是我刷的第一道,剛一開始的Java實現
public int[] twoSum(int[] nums, int target) {
boolean find = false;
int targeti = -1, targetj = -1;
for (int i = 0; i < nums.length; i++) {
for (int j = 0; j < nums.length ; j++) {
if (i == j) {
continue;
}
if (nums[i] + nums[j] == target) {
targeti = i;
targetj = j;
find = true;
break;
}
}
if (find) {
break;
}
}
return new int[]{targeti, targetj};
}
稍微改進一下
public int[] twoSum(int[] nums, int target) {
boolean find = false;
int targeti = -1, targetj = -1;
for (int i = 0; i < nums.length - 1; i++) {
for (int j = i + 1; j < nums.length; j++) {
if (nums[i] + nums[j] == target) {
targeti = i;
targetj = j;
find = true ;
break;
}
}
if (find) {
break;
}
}
return new int[]{targeti, targetj};
}
下面這個版本是在討論中看到的O(1)時間復雜度
public int[] twoSum3(int[] nums, int target) {
int[] result = new int[2];
Map<Integer, Integer> map = new HashMap<Integer, Integer>();
for (int i = 0; i < nums.length; i++) {
if (map.containsKey(target - nums[i])) {
result[1] = i;
result[0] = map.get(target - nums[i]);
return result;
}
map.put(nums[i], i);
}
return result;
}
1. Two Sum - LeetCode