标签:两数之和 int ash contains hashmap integer exce == 数组
暴力枚举法
直接两重循环暴力枚举,很慢。
class Solution {
public int[] twoSum(int[] nums, int target) {
int[] ans = new int[2];
for(int i = 0; i < nums.length; i++) {
for(int j = i + 1; j < nums.length; j++) {
if(nums[i] + nums[j] == target) {
ans[0] = i;
ans[1] = j;
break;
}
}
}
return ans;
}
}
哈希表思想
为原数组建立哈希索引表map,之后只需在哈希表中找到target-nums[i]的目标元素坐标即可。
class Solution {
public int[] twoSum(int[] nums, int target) {
Map<Integer, Integer> map = new HashMap<Integer, Integer>();
for(int i = 0; i < nums.length; i++) {
if(map.containsKey(target - nums[i]) && map.get(target - nums[i])!=i) {
return new int[] {map.get(target - nums[i]), i};
}
map.put(nums[i], i);
}
throw new IllegalArgumentException("now two sum solution");
}
}
标签:两数之和 int ash contains hashmap integer exce == 数组
原文地址:https://www.cnblogs.com/fromneptune/p/13234854.html